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Full text of "Science (Std10 - English Medium)"

S.No. CONTENT Page No. 

BIOLOGY 

1. Heredity and Evolution 1 

2. Immune System 15 

3. Structure and Functions of Human Body-Organ systems 33 

4. Reproduction in Plants 51 

5. A Representative Study of Mammals 73 

6. Life Processes 87 

7. Conservation of Environment 105 

8. Waste Water Management 121 
CHEMISTRY 

9. Solutions 133 

10. Atoms and Molecules 143 

11. Chemical Reactions 153 

12. Periodic Classification of Elements 174 

13. Carbon and its Compounds 194 
PHYSICS 

14. Measuring Instruments 211 

15. Laws of Motion and Gravitation 216 

16. Electricity and Energy 232 

17. Magnetic Effect of Electric Current and light 254 
Syllabus 286 
Practicals 291 



III 



Chapter 






HEREDITY 

AND EVOLUTION 




1. HEREDITY AND EVOLUTION 



HEREDITY AND VARIATION 

A cow gives birth to a calf. Both the 
mother cow and calf share common 
characteristics like body design, 
physiological function etc, that are specific 
to their species. However on a very close 
observation of the mother cow and the 
calf and the bull which is the calf's other 
parent , we will come across a number 
of differences among them, like colour 
pattern in the skin. By virtue of being 



ACTIVITY 1.1 



Ask your classmates to roll their 
tongues. Observe how many can 
and how many are not able to roll 
their tongues. Record your findings. 

Similarly record the variation in the 
eye colour noticed among your 
classmates. 



the progeny of the parent, the progeny 
individual, need not just be the replica 
of what its parents are. (Inheritance 
of characters from the parents to the 
progeny ( i.e. , Heredity) ensures the 
passing of the parental characters to the 
progeny). The difference or change in the 
characteristics between the individuals 
is called Variation. Human population 
shows a great deal of variation. 

1-1- HEREDITY 

The progeny produced through the 
reproductive process is similar to its 



parents, in body design, function etc.. The 
rules of heredity determine the process 
by which the traits and the characteristics 
are relatively inherited. 

"The inheritance of characteristics 
through generation is called heredity" 

The inheritable characteristics may be 
morphological/anatomical/physiological/ 
reproductive and are also known as 
traits. 

If we take a very close look at the 
rules of inheritance, both father and 
mother contribute equal amount of 
genetic material to the child. This means 
that each trait can be influenced by 
both paternal and maternal genetic 
material - i.e, DNA. 

Gregor Johann Mendel (1822-1884) 
worked out the first ever scientific 
experimental study on heredity. 

Mendel, an Austrian Augustinian monk 
observed variations in the characteristics 
of garden pea plant (Pisum sativum) 
which he had cultivated in his monastery 
garden. Mendel was curious to find out 
the results of crossing of pea plants 
with the variation in traits. The visible 
contrasting characters that Mendel 
observed in the garden pea plants were 



Seed shape 
Seed colour 
Flower colour 



Round/Wrinkled 
Yellow/Green 
Violet /White 



HEREDITY AND EVOLUTION 




Character Dominant trait 



Seed shape ' 

Round 




Seed colour 

Yellow 

< '■ ) 

Flower colour / / 
Violet 



Full 



Pod colour 



Green 



Flower 
Position 




Stem 
height 



Recessive trait 



Wrinkled 



Green 




White 



Pod shape ^^^ ^^m 

CM Constricted 



/ / 



Yellow 




"^j 



Terminal 



3 

^ 



Tall Dwarf 

F\g. 1.1 Seven pairs of contrasting 
traits in Pea plant studied by Mendel. 



Pod shape 
Pod colour 



Full / Constricted 
Green /Yellow 



• Flower position - Axillary /Terminal 

• Stem height - Tall / Dwarf 

l.l-l- Mendel's monohybrid cross 

Mendel selected the garden pea plant, 
Pisum sativum for his experiments. He 
selected tall and dwarf plants and allowed 
them to grow naturally. As pea plants 
produce seeds only by self pollination, he 
observed that tall plants produced always 



Parental 



I 



f '•^ 



Tall 



Dwarf 



i 



F^ generation Zp -^ % 

7^11 Selfing Tall 
F^ generation 




Tall Tall Dwarf 



Fig. 1.2 Diagrammatic representation of 
Monohybrid cross 

tall plants generation after generation 
under natural condition. Similarly, dwarf 
plants produced always dwarf plants 
generation after generation. Hence, he 
termed the tall and dwarf plants as wild 
types or pure breeding varieties. 




Then he crossed a tall plant with 
a dwarf plant, produced progeny and 
calculated the percentage of tallness and 
dwarfness in subsequent generations. 

When a pure breeding tall plant was 
crossed with a pure breeding dwarf 
plant, all plants were tall in the first filial 
generation (Fl) i.e., there was not any 

Gregor Johann Mendel(1822-1884) 

Mendel was 

educated in a 
monastery and went 
on to study science 
and mathematics 
at the university of 
Vienna. Failure in the 
examinations for a teaching certificate 
did not suppress his zeal for scientific 
quest. He went back to his monastery 
and started growing peas. Many others 
had studied the inheritance of traits 
in peas and other organisms earlier, 
but Mendel blended his knowledge of 
Science and Mathematics and was the 
first one to keep count of individuals 
exhibiting a particular trait in each 
generation. This helped him to arrive 
at the laws of inheritance that we have 
discussed in the main text. 




ACTIVITY 1.2 



Observe in your locality for plants 
which show different characters for 
the following traits. Count them and 
record your findings. Examples: 


Coconut 


Tall 


Dwarf 


Bean 


Violet Flower 


White Flower 


Sugarcane 


White Stem 


Purple Stem 


Clitoria 


Blue Flowers 


White Flowers 





medium height plants or dwarf plants. 
This means that only one of the parental 
traits were seen and not the mixture of 
the two. When such a Fl tall plant was 
allowed to have self pollination, both the 
tall and dwarf plants appeared in second 
filial generation (F2). in the ratio of 3:1. 
This indicates that both tallness and 
dwarfness were inherited in the Fl plants 
but only tallness trait was expressed. 

The first experiment of Mendel 
considering the inheritance of a single trait 
(Height of the plant Tall/Dwarf) is called 
Monohybrid Cross. 

Expression of morphological 
characters as tall or dwarf plant, violet or 
white flower is called Phenotype. 

The expression of gene (or 
Chromosomal make up) of an individual 
for a particular trait is called Genotype. 

1.1.2. Physical basis of heredity 

The genotype of a character is 
influenced by factors, called Genes. 
The genes are the factors which form 
the physical basis for inheritance of 
Characters. The alternate expressions 
of the same gene are called alleles. 
The contrasting pair of alleles make 
up an allelomorph. Examples : Tall and 



Leaves 



Buds and Fruit 




, Seeds 



Insects^^ 





Grubs 



Fig. 1.3 Variations in tine beaks offincties 
to suit their eating inabits. 



HEREDITY AND EVOLUTION 




ACTIVITY 1.3 



Find out identical / Non-identical twins 
in your school and locality. Find the 
minute variations between them. 

dwarf plants, wrinkled and smooth seed 
coat, white and violet coloured flower. 
Organisms differ or vary in expressing 
phenotype which leads to variation. 

1-2- VARIATION 

All around us , we see different 
organisms belonging to different species, 
differing from one another. Variation 
may be defined as the differences in the 
characteristics among the individuals 
of the same species (intra specific 
variation) or among the different genera 






Fig. 1.4 Identical twins 

(intergeneric variation) or different 
species (Inter specific Variation). No two 
individuals are identical to each other. 
Asexual reproduction produces, very 
closely resembling offsprings. Asexual 
reproduction thus results in offsprings with 
minor variations. Sexually reproducing 
organisms produce offsprings with 
marked, significant and visible variations. 

1.2.1. Types of variations 

a. Somatic Variation - It pertains to 
bodycells and it is not inherited. 




Charles Darwin: (1809-1882) Charles 

Darwin set out on a voyage when he was 

22 years old. The 5 year voyage took him 

to South America and the islands, off its 

coast. Interestingly 

after he got back 

to England, he 

never left to the 

shores again. He 

stayed at home and 

conducted various 

experiments that 

led him to formulate 

his hypothesis 

from which evolution took place due to ral 

selection. He did not know the mechanism 

from where the variations arose in the 

species. Had he been enlightened by 

Mendel's experiments, he would have 

contributed more. But these two great men 

did not know of each other or of their works! 

We often associate Darwin solely with 
the theory of evolution. But he was an 
accomplished naturalist, and one of the 
studies he conducted was, to do with the 
role of earthworms in soil fertility. 



b. Germinal Variation - It pertains 
to germ cells or gametes and it is 
inheritable. It leads to speciation 
and evolution. 

Significance of Variation 

♦ It is the source of raw material for 
evolution. 

♦ Animals are able to adapt themselves 
to the changing environment. 




Lamarckian 
View on organic evolution: 




Fig. 1.5 Giraffe 
Jean Baptise Lamarck (1744-1829) 
postulated the Use and Disuse Theory. 
According to Lamarck, use of a part 
/ organ efficiently by a species, for 
generations over a long period of time, 
results in that part / organ being well 
developed in the subsequent generations 
and disuse of part/organ for a long period 
would make that part / organ diminished or 
degenerated. 

Lamarck quotes the example of 
development of long neck of Giraffe. 
Giraffes were forced to extend their neck 
and stretch their legs to reach the leaves of 
tall trees. Over a long period of time, this 
resulted in long neck and legs in giraffe. 
Lamarck remarks that the "will or want" 
for a character makes the organisms to 
posseses it at a later time. 

♦ Organisms are better suited to face 
the struggle for existence 

♦ Variations give the organisms an 
individuality of their own. 

♦ Without variation, there would be no 
science of heredity as all individuals 



of a race, would be identical in all 
aspects. 

1.2.2. Theory Of Natural Selection 

Charles Darwin made a number of 
observations in many parts of the world 
and put forth the law of natural selection 
involving struggle for existence and 
survival of the fittest. 

Variation leads to genetic 
diversity,which is the key for evolution. 

1.3. EVOLUTION 

Evolution may be defined as a gradual 
development of more complex species 
from pre-existing simpler forms. 

It is an extremely slow process and 
has occurred over millions of years, as 
revealed by fossil evidences. 

Evolution has thus resulted in the 
diversity of organisms, influenced by 
environmental selection. 

1.4. SPECIATION 

Mankind in India and all other parts 
of the world, form a single species 
called Homo sapiens. As in India, 
morphological features of people living 
in different geographical areas like 
South India, North India, North Eastern 
region, Kashmir and Andaman are not 
the same as the people living in different 
continents are different in morphological 
features. 

Men, with these differences in their 
bodily features, differentiate more 
and more, if there is no chance of 
interbreeding among them. 

Imagine a situation, where this 
would result in the impossibility of 



HEREDITY AND EVOLUTION 




breeding between two such individuals 
of geographically isolated populations. 
Then they would be ready to become 
two different species. 

When two populations are isolated by 
geographical barriers, or reproductive 
barriers, there is a chance for a change to 
develop in their gene flow (Genetic drift), 
leading to formation of a new species. 
Genetic drift with changes in the gene 
flow imposed by isolation mechanism 
acts as an agent of speciation. 

Thus speciation is arising of a new 
species from a sub-population of a 
species which is geographically or 
reproductively isolated over a long period 
of time from the other population of the 
same species. 








Fig. 1.6 A comparison ofttie s/ci///s of adult 

modern human being, baby chimpanzee 

and adult chimpanzee. The skull of baby 

chimpanzee is more like adult human skull than 

adult chimpanzee skull. 



1-5- HUMAN EVOLUTION 

Fifteen million years ago, in Africa 
existed hairy bodied Gorilla and 
Chimpanzees like Hominids. After that 
3-4 million years ago, men like hominids, 
walked into Eastern Africa. Evidence 
shows that they hunted with stone 
weapons but were mostly fruit eaters. 
They were probably not taller than four 
feet but, walked upright in the grass 
lands of East Africa. These creatures 
were called the First human like being 
- the hominid. The hominid was called 
Homo habilis. 

The next stage of human evolution 
came into existence 1.5 million years 
ago with the rise of Homo erectus who 
were meat eaters 

The Neanderthal man who lived in 
East and Central Asia 1 million years 




Fig. 1. 7 Evolutionary tree 




ago, used to hide to protect them and 
buried their dead. 

Archaic Homo sapiens arose in South 
Africa and moved across continents and 
developed into distinct races during the 
ice age. Between 75,000 - 10,000 years, 
the modern Homo sapiens arose. Pre- 
historic caves were developed about 
18,000 years ago, agriculture came 
around 10,000 years back and human 
settlements started. 

1-6- EVOLUTION TREE 

To understand evolution, a branching 
diagram or "Tree" is used to show the 
inferred evolution, relationships, among 
various biological species or other entities 



based upon similarities and differences in 
their physical and genetical characters. 

1,7, GENETIC ENGINEERING 

Genetic engineering is the modification 
of the genetic information of living 
organisms by manipulation of DNA by 
adding, removing or repairing part of 
genetic material (DNA) and changing the 
phenotype of the organism. It is also known 
as gene manipulation or recombinant DNA 
Technology (r-DNA Technology) 

Recent advances made in Genetics, 
Molecular Biology and Bio-Chemistry 
have resulted in the origin of this new 
branch of science. The benefits derived 
through the Genetic Engineering include: 



%i 



Medical products 

1. Insulin 

2. Growth hormone 

3. Vaccines 

4. Antibiotics 

5. Monoclonal 
antibodies 




Genetic engineering 

1. Transgenic plants 

2. Transgenic animals 




Microbial metabolites I 

1. Enzymes 

2. Vitamins 

3. Steroids 

4. Ethanol 



5 



Scope of 
o-technolog 



t5 



Mining 
Mineral extraction 



T 



Waste treatment 
^ ^ ^ 1. Sewage 
^ 2. Toxic wastes 

^ 3. Waste oil 

\4 4. Agricultural wastes 



I 



^ 



«. 



Organic acids 

1. Acetic acid 

2. Citric acid 

3. Butyric acid 



a 



rn 



Fruit and Drink 

1. Dairy product 

2. Brewing 

3. Baking 

4. Single cell protein 



^ 



HEREDITY AND EVOLUTION 




♦ Understanding of the gene structure 
and function through basic research. 

♦ Production of large quantities of 
insulin, interferon(Anti-Viral Protein 
produced by Virus infected cells) 
human growth hormones, proteins 
(Polypeptides) and vaccines for foot 
and mouth disease of cattle (komari - 
in Tamil) etc., 

♦ This technique is also employed in the 
transfer of genes involved in Nitrogen 
fixation(NF-genes). This will help the 
cultivator to increase productivity. 

1.7.1. Basic techniques in Genetic 
Engineering 

Genetic Engineering has developed 
after the discovery of two enzymes. 
The enzymes which can cut DNA into 
fragments, and enzymes which can join 
such fragments. 

Restriction enzymes or Restriction 
endonucleases are molecular scissors 
which cut DNA at specific sites. DNA 
ligases are the paste enzyme which 
helps to join the broken DNA fragments. 



1.8. BIO-TECHNOLOGY 
CLONING 



AND 



Bio-technologyhascontributedtowards 
exploitation of biological organisms or 
biological processes through modern 
techniques which could be profitably 
used in medicine, agriculture, animal 
husbandry and environmental cleaning. 
There are several applications of 
Bio-technology such as brewing Industry, 
enzyme technology, manufacturing of 




It was Edward 

Jenner (1749- 

1823) in 1791 

who coined the 

term vaccine 

and the term 

vaccination 

for protective 

inoculation. 

Vaccines 

produced by Edward Jenner 

Bio-technology differ from others. In that, 

they do not contain weakened or killed 

agents. Instead they are so refined as 

to consist only the reactive material ie., 

the antigen protein only. The first such 

vaccine was used against Hepatitis B 

Virus (HBV) 

anti-biotics, organic acids, vitamins, 
vaccines, steroids and monoclonal 
anti-bodies. 

Brewing Industry: Fermentation in 
alcoholic beverages like beer, wine etc.. 

Enzyme Technology : Enzymes are 
bio-catalysts that speed up reaction in 
cells. They can be used to catalyze the 
industrially important reactions and are 
more efficient than inorganic catalysts. 
Many enzymes are utilized in the 
pharmaceutical industry. 

Anti-Biotics : These are substances 
produced by some microbes that 
help in increasing the immunity to 
human beings which are toxic to other 
micro-organisms. 

Organic Acids: Acetic acid is used for 
the production of vinegar. 




Development of Dolly 




Cloning 
Dolly was a cloned sheep, developed 
by Dr.lan Wilmut and his colleagues in 
Roselind Institute in Scotland in July 
1996. 

The scientists used nucleus of udder 
cell (somatic cell taken from mammary 
gland) from a six year old Finn Dorset 
white sheep. 

The nucleus of the udder cell contains, 
diploid number(2n) of chromosomes with 
all the genes. They preserved the diploid 
nucleus in a suitable preservative. Then 
they took an ovum from the ovary of 
another sheep. The haploid nucleus (n) 
in the ovum was removed. 

The diploid nucleus of the udder cell 
was injected into the cytoplasm of the 
enucleated ovum. Then the ovum with 
the diploid nucleus, was implanted into 
the uterus of the surrogate mother sheep. 
Since the ovum had the diploid nucleus, 
it developed into a young clone. It was 
named "Dolly" by Dr.lan Wilmut. 

Vitamins: These are chemical 
compounds present in variable minute 
quantities in natural food stuffs. They do 







Fig. 1.10 Dr. Ian Wilmut with dolly 

not furnish energy but are very essential 
for energy transformation and regulation 
of metabolism. 

Vaccines: Vaccines are substances 
that confer immunity against specific 
disease. Theyactas antigens and stimulate 
the body to manufacture antibody. 

Steroids: They are a type of derived 
lipids Ex: Cholesterol, containing steroid 
drugs like prednisolone is produced from 
fungus Rhizopus. 

Monoclonal anti-bodies : These are 
the anti bodies produced by cloned cells. 
Monoclonal anti -bodies, are now used 
for treatment of cancer. 

Cloning: Cloning is an experimental 
technique wherein a group of 
morphologically and genetically identical 
organisms are produced. The "Clone" 
is an organism derived from a single 
parent by asexual method. A clone may 
be defined as an exact carbon copy or 
copies of a single parent. 

The word clone refers only to living 
species. 

If the cloning technique is to be 
applied to veterinary science, valuable 



HEREDITY AND EVOLUTION 




animals could be cloned from desirable 
adult cells. 

1.8.1 Types of Clones 

Natural clones: The natural clones 
include identical twins. 

Induced clones: The induced 
(artificial) clones are developed by 
nuclear transfer into the host cell 

1.9. STEM CELL (ORGAN) 
CULTURE: 

One of the most fascinating branches 
in applied embryology is stem cell 
culture. The stem cells are the most 
unspecialized mass of cells. They 
are derived from animals and plants. 
They have two important characteristic 
features. They are: 

1. Unspecialized cells which have the 
potentiality of growing and multiplying 
into enormous number of same type of 
cells by repeated mitosis. 

2.They can be introduced to become 
any other type of tissues with specific 
functions i.e., they can be induced to 
become a cardiac muscle, beta cells 
of pancreas (which produce insulin), 
special neurons in brain etc., 

1.9.1. Types of Stem Cells 

There are two kinds of stem cells 

1. Embryonic Stem Cells: The 

embryonic stem cells can be derived 
from early embryo which is developed 
by "invitro fertilization" (fertilisation made 
artificially in the laboratory). 

After fertilization the zygote develops 
into a hollow blastula by cell division. 



The inner mass of undifferentiated cells 
are isolated and they are considered as 
embryonic stem cells. 

2. Adult or Somatic Stem Cells: 

The body of higher animals and human 
beings have many well differentiated 
tissues like epithelial, connective, 
muscular, vascular, supporting, nervous 
and reproductive tissues. In these tissues, 
there are some undifferentiated cells and 
are considered as the adult or somatic 
stem cells. They can grow, multiply and 
can be differentiated into same type of 
tissues into which they are implanted. 
The mechanism of adult or somatic stem 
cell culture is similar to that of embryonic 
stem cell culture. The somatic stem cells 
are derived from sources such as bone 
marrow, embryos, amniotic fluid and 
umbilical cord. 

1.10. MICROBIAL PRODUCTION 

As we discussed earlier, the field of 
Bio-technology is so vast and has great 
scope for different fields like agriculture, 
medicine, foodindustry etc.. 

The microbial products of every day 
use are: 

Vaccines : Killed or live germs 
suspension which is employed to induce 
the production of antibodies and bring 
forth immunity. 

Antibiotics : Antibiotics are chemical 
substances derived from microbes like 
fungi, bacteria etc., employed to kill the 
infectious germs and cure a disease. 

Vitamin B^^ : Bio technologically 
synthesized vitamin B^^ '^ used, to cure 
pernicious anaemia. 




t 



2. In the laboratory, a virus 
is altered so that it cannot 

1. Cells are removed reproduce.^ 

from patient 




7. The geneticaliy^ — ^. 
altered cells 
produce the desired 
protien or hormone. 



\f^ 



6.The altered cells 
are injected into the 
patient. 



^ 



'^. A gene 

i isjnserted 

nto the 



V 





5. The cells from 
the patient become 
genetically altered . 

Fig 1.11 Gene therapy 



4. The altered virus 
is mixed with cells 
from the patient. 



Enzymes : Bio-Chemically significant 
enzymes are derived from microbes \ Ex. 
Amylase is derived from amyloproteins 
of bacteria. 

Insulin : Diabetes is treated by the 
biotechnologically produced insulin. 

1,11, BIO-SENSOR AND 
BIO-CHIPS 

Bio sensor: It is a device consisting 
of immobilized layer of biological material 
such as enzyme, antibody, hormone, 
nucleic acids, organelles or whole 
cells and its contact with a sensor. The 
sensor converts biological signals into an 
electrical signal. It is used in medicines 
and industry. 



Blood glucose level can 
detected. 



be 



2. Production of any toxin in the body 
due to infection can be detected. 

3. Pollution in drinking water can be 
monitored. 

4. Odour, freshness and taste of food 
can be measured. 



Bio-Chips 

Bio-Chips are microchips which are 
developed by employing techniques 
of Bio-technology. In future, biological 
computers will be developed using 
bio-chips. Bio-Chips will be useful in 
defence, medicine etc.. 



1,12 SCIENCE TODAY 
THERAPY 



GENE 



Insulin dependent diabetes is 
treated with insulin injection. Insulin 
dependent diabetes is caused by the 
degeneration of beta cells due to a 
defective gene. Applying the principle 
of Bio-technology, it is possible to 
correct the defective gene. When the 
defective gene is corrected with a new 
gene, the genetic defect developed is, 
rectified and cured. 

Gene Therapy is the means to treat 
or even cure genetic and acquired 
diseases like cancer and Aids by using 
normal gene to supplement or replace 
the defective gene. 

It can be used to treat defects in 
Somatic i.e., (body) or Gametic (sperm 
or eggs) Cell. 

Types of Gene Therapy 

1. Somatic gene therapy:- The 
genome (gene set) of the 
recipient is changed. But this 
change is not passed along to 
the next generation. 

2. Germ line gene therapy:- Egg 
and sperm of the parents are 
changed, for the purpose of 
passing the changes to the next 
generation. 



HEREDITY AND EVOLUTION 




EVALUATION 



PART A 

1. Mendel observed 7 pairs of contrasting 
characters in Pisum sativum. One 
of the following is not a part of that. 
Find out. 

• Tall and dwarf, 

• Yellow and green seed colour, 

• Terminal and axial Flower, 

• Smooth and rough stem 

2. Primitive man evolved in - (Africa, 
America, Australia, India) 

3. Which of the following is inheritable 
(an altered gene in sperm, analtered 
gene in testes, an altered gene in 
zygote ,an altered gene in udder cell) 

4. Theory of natural selection was 
proposed by - (Charles Darwin, Hugo 
de Vries, Gregor Johann Mendel,Jean 
Baptise Lamarck) 

5. Somatic gene therapy (affects sperm, 
affects egg, affects progeny , affects 
body cell) 

PART B 

6. Mendel has observed Tallness as 
dominant character in Garden pea 
plant. Similarly tongue rolling is a 
dominant character in man. In a group 
of 60 students, 45 can roll their tongue 
and 15 are non rollers. 

a) In the above context, calculate 
the percentage of dominant and 
recessive characters. 

b) In Garden pea plant, draw the 
diagrammatic representation of 
mono hybrid cross as explained by 
Mendel. 



7. The heritable characters are varying 
in different species and within the 
same species. 

Name the variation in the following cases. 

The eye colour among the human 
beings are varied as blue, black, 
brown, green, etc.. 



variation. 



a) This is called as 

The dentition in rabbit and 
elephant are not the same. 

b) This is called as 

variation. 

8. Sexually reproducing organisms 
produce offsprings with marked, 
significant and visible variation. 

Asexually reproducing offsprings 
show minor variations. 

a) Do you agree with the above 
statements? 

b) Among the following organisms 
list out the asexually reproducing 
organisms. 

(Paramoecium, Euglena, 
Earthworm and Bird). 

9. Here is a certain important hereditary 
jargons, fix a suitable one from the list 
given below. 

a) are the factors 

which form the physical basis of 
inheritance. 

b) is alternate expression 



of same gene. 



c) are contrasting pairs of 

alleles. (alleles, variation, speciation, 
gene, allelomorph) 




10. A change that affects the body cell 
is not inherited. However , a change 
in the gamete is inherited. Radiation 
effects of Hiroshima has been 
affecting generations. Analyzing 
the above statements, give your 
interpretation. 

11. Sequentially arrange the different 
species of man from primitive to 
modern man. (Neanderthal man, 
Homo habilis. Homo erectus. Homo 
sapiens) 

12. Bio-technology , the modern science 
in biology, has helped in producing 
different types of products. 

One of the following group does not 
have a product of bio-technology. 
Pick out and give reasons. 

a) Enzymes, Organic acids. 
Steroids, Vaccines 

b) Vaccines, Enzymes, Anti 
biotics. Organic acids 

c) Anti biotics. Hormones, 
Steroids, Vaccines 

d) Steroids, Enzymes, Anti bodies. 
Vaccines. 

13. Identical twins are syngenic with 
similar chromosomal contents. 
Natural clones are those who 
possess identical chromosomes. Fill 
up with the suitable word given in 
the bracket. 



a) Identical twins are 

(Natural clones/ Induced clones) 

b) Identical twins are 

(dissimilar to each other / similar 
to each other). 

14. The ancestor of particular type of frog 
found in India and Srilanka were the 
same. 




a) With reference to the above map, 
identify the factor that has resulted 
in the formation of a new species. 

b) State a few other factors that help in 
the formation of new species. 

PART C 

15. Human evolution has a record of 
changes for the past of 15 milion 
years. 

a) Name the different species of 
mankind in chronological order 
from primitive to modern man. 

b)When were the primitive caves 
developed.? 

c) Narrate the life led by early man like 
hominids. 



FURTHER REFERENCE 

Books: 1. Biology- A Modern Introduction B.S.Beckett, Second Edition, 
Oxform University Press 



Chapter 






IMMUNE 
SYSTEM 



^ 



2. IMMUNE SYSTEM 



IMMUNE SYSTEM 

"Health is Wealth" is an apt proverb. 
There can be no wealth greater than 
the good health that a person enjoys. In 
a healthy state, a person keeps himself 
physically, mentally and socially, fit. Our 
body has a complex defense mechanism 
to keep itself fit and work against various 
agents which disturb our well being. 
Being exposed to diseases, we develop 
resistance towards diseases and gain 
immunity. 

2,1, HEALTH AND ITS SIGNIFICANCE 

"Health is a state of physical, mental and 
social well being of an individual and not 
merely absence of a disease or infirmity". 

When a person is in good health, the 
different organ systems, not only function 
well discharging their duties, but the body 
as a whole is also able to adjust itself and 
strike a balance with the physical, mental 
and social environments. 

The varying environmental factors such 
as temperature, humidity, wind, pressure, 
sun, rain, pollution caused by man, atomic 
radiation, malnutrition, the millions of 
microbes that surround our bodies, the 
inter-personal conflicts are all other factors 
affect our lives and are challenges to our 
health. 

Dimensions of Health 

1. Physical dimension : A person who 
is free from disease, is bright with 
his skin shining enjoying normal 
metabolism, has a good lustrous hair 



and has no black rings around his 
eyes. 

Mental dimension : A mentally 
healthy person who knows his 
capacities, does not overestimate or 
underestimate himself and can judge 
his shortcomings and weaknesses. 

Social dimension : A person 



Physical ^ 
Well being 




Mental 
Well being 



{ 



Social 
Well being 



F\g. 2.1 Dimensions ofhealtli 

adjusting himself in society, does not 
find fault with others. He maintains 
interpersonal relationships with his 
family members and colleagues at 
workspotand is free from interpersonal 
conflicts and will not quarrel. 



IMMUNE SYSTEM 




ACTIVITY 2.1 



Following the above criteria, make a 
survey of your classmates/people in 
your neighbourhood and record your 
finding 

• Number of students/neighbours who 
are healthy. 

• Number of students/neighbours who 
do not have good interpersonal 
relationship and do not enjoy so- 
cial well being. 

• Number of students/neighbours who 
have diseases affecting their me- 
tabolism. 

• List out positive qualities that you 
admire in your friend. 



Genetical 



2-2- DISEASES AND CAUSES 

The word disease means, "without 
ease or not at ease" and it is opposite to 
health. The condition of malfunctioning 
of the organ system or systems is called 
disease. There are numerous diseases 
that damage our health. 

Causes of the diseases 

Diseases are caused due to various 
factors such as pathogens, environmental 
factors, nutritional factors, genetic factors, 
metabolic factors, etc. 

Based on the causative agent, diseases 
are classified into: 

1. Diseases not caused by organisms 

2. Diseases caused by organisms 



Nutritional 



^ J^f^^ Environmental 




Metabolic 



Pathogens 



Fig. 2.2 Causes of diseases 

Diseases not caused by organisms - 
Non communicable diseases 

1. Organic diseases or Metabolic 
disorders: Healthy body maintains a constant 
blood sugar level which is normally 80- 
120 mg / 100 ml of blood under, fasting 
conditions. When large quantities of glucose 
enter the blood stream, as it happens after 
a meal, the excess glucose is converted into 
insoluble glycogen and stored in liver and 
muscles for future use. Later when required, 
glycogen is reconverted into glucose and 
reintroduced into blood stream. All these 
processes are controlled by the hormone. 
Insulin, secreted by beta cells of Islets of 
Langerhans of Pancreas. If Insulin is not 
produced in sufficient quantity, excess of 
sugar cannot be stored and utilized. As a 
result, sugar continues to get accumulated 
in the blood, till it is lost through urine. This 
leads to other complications and results in 
diabetes mellitus. Diabetes mellitus is a state 
of expulsion of excess unused glucose in the 
urine due to less production of insulin. 

Similarly, Diabetes Insipidus, Coronary 
heartdiseases. Renal failure. Hypertension, 



^ 



Obesity, Alzheimer's disease, Stroke 
affecting the functions of the brain, etc, are 
all caused due to metabolic disorders. 

2. Hereditary diseases or Genetical 
disorders: The genetical disorders are 
caused due to defective or mutated 
genes. Albinism is an inherited disorder 
of melanin metabolism, characterized by 
the absence of melanin in the skin , hairs 
and eyes. The recessive mutant genes 
cause this disorder. The clinical symptoms 
of Albinism are milky white coloured skin 
and marked photophobia (high sensitivity 
to light). Haemophilia, sickle cell anaemia. 
Thalassemia, Down's syndrome. Bubble 
boy syndrome, etc,, are a few other 
genetical disorders. 

3. Nutritional Deficiency Diseases: A 

diet which contains all essential nutrients 
in correct proportion, is indispensable for 
maintaining good health. Deficiency in 
certain food constituents, causes various 
kinds of diseases. Protein deficiency 
causes Marasmus and Kwashiorkar. In 
Marasmus, the child loses weight and 
suffers severe diarrhoea and it will appear 
as though bones are covered by the 
skin. In Kwashiorkar the child develops 
an enlarged belly with swelling in the 
face and feet. 



4. Diseases caused by Organisms: 

Robert Koch and Louis Pasteur were 
the first to establish the Germ theory of 
diseases. A germ or microbe gains entry 
into the host, such as man, multiplies so 
fast that it can increase in large numbers, 
produce poisonous substance called Toxins 
and interfere with the host metabolism and 
produce a characteristic set of symptoms 
by which the disease can be diagnosed. 

Disease producing organism 





Fig. 2.4 Kwashiorkar 




Fig. 2.3 An albino 



Fig. 2.5 Marasmus 



IMMUNE SYSTEM 




SOME IMPORTANT VITAMIN DEFICIENCY DISEASES ARE TABULATED BELOW: 



Vitamin 






^ficiency disease 




J 


nptoms 


tf 


Vitamin A 


Nyctalopia 


Night blindness 


Vitamin B^ 


Beri-Beri 


Nervous disorder 


Vitamin B^ 


Pellagra 


Dementia, dermatitis, 
diarrhoea 


Vitamin B^^ 


Pernicious anaemia 


Destruction of RBC 


Vitamin C 


Scurvy 


Bleeding gums and 
loosening of teeth 


Vitamin D 


Rickets 


Defective calcification of 
bones 


Vitamin E 


Sterility 


Inability to reproduce 


Vitamin K 


Haemorrhage 


Profuse loss of blood 



1. Parasitic Micro-organism: The 

causative organism of a large number of 
diseases in man, are micro-organisms 
belonging to different groups. They are 
viruses, bacteria, fungi and protozoans. 

2. Viruses and viral diseases in man: 

Viruses are living substances inside the 
host cell and behave as dead particles 
outside the host cell. The Viral body 
consists of a nucleic acid, DNA or RNA and 
a protein cover. All the known viruses are 
parasitic and some of them cause deadly 
diseases such as. polio, rabies, hepatitis, 
meningitis, encephalitis (brain fever), etc. 

3. Bacteria and Bacterial Diseases: 



Bacteria are unicellular prokaryotes and 
visible under Compound Microscope. 
Though many bacteria are harmless, 
some are parasitic and produce diseases. 
Bacteria can enter the host body through 
the mouth, nostrils or cuts and bruises on 
the skin. They multiply rapidly, producing 
toxins in high concentration to affect 
health. Some bacterial diseases in man are 
Tuberculosis, Leprosy, Cholera, Typhoid, 
Diphtheria, Tetanus, Plague, Pneumonia, 
Syphilis, Gonorrhoea, etc. 

Fungi and Fungal Diseases: Fungi 
are non green saprophytic or parasitic 
plants living on dead and decaying organic 
matter or living organisms. Certain species 



^ 



of fungi are parasitic on man and cause 
Ringworm attacking the keratinized layer 
of skin, destroying it in circular patches. 




Fig. 2.6 Bacilli 

Dandruff, Athletes' foot are some other 
fungal diseases in man. 



Protozoan and Protozoan Diseases: 

Protozoans are unicellular animalcules, 
some parasitize man and cause diseases 
such as malaria, amoebic dysentery, 
sleeping sickness, etc. 

Parasitic macro-organisms: 

Infestations of the body with tapeworm, 
liver fluke, round worm, filarial worm, etc,, 
cause diseases in man like Taeniasis, 
Ascariasis, Filariasis, etc,. 

2,3- DISEASES CAUSED BY 
MICROBES AND 
PREVENTION 

A disease caused by a parasitic 
organism and transmitted from one person 
to another by the transfer of the parasite is 
known as infectious disease. 

We shall study the cause, spread and 
prevention of a few selected infectious 
diseases prevalent in our country so that 
we will know how to guard ourselves 
against them and other similar diseases. 




-RNA Capsomere 

DNA 



— Capsomere 
^ ofcapsid 



.m. 




Membranous 

envelope *^^^ 

Head ^ EL 

Tail 




Sheath 



1-- 

- — Glycoprotein r ^ - 

Glycoprotein 



Capsid 





DNA 



Tail 
Fiber 



(a) Tobacco (b) Adeno viruses (c) Influenza viruses (d) Bacteriophage 

mosaic virus 

Fig. 2.7 Types of Viruses 



IMMUNE SYSTEM 




2.3.1. Viral diseases 

2.3.1.1. Common Cold 

More than hundred strains of viruses 
are responsible, for causing common cold 
in man. Children are more susceptible to 
common cold than adults. 

Symptoms 

1. Inflammation of upper respiratory 

passage - nasal epithelium. 

2. Flow of mucous. 

3. Headache, slightrise in temperature, 
etc,. 

It lowers the resistance of the body, 
leading to a number of secondary infections 
like pneumonia, bronchitis, etc,. 

Transmission 

i) It spreads mostly through the droplets 
discharged from the nose and the 
mouth of the patient in the process of 
talking, laughing, sneezing, etc,. 

ii) It may also spread through close 
inanimate objects like handkerchief. 




Fig. 2.8 Human rhino virus 

bedding, clothes, utensils, 
articles, etc,, (called fomites) 



Control and prevention: There are 
no effective measures to control common 
cold. However, a good nourishing food, 
avoiding contact with patients and wearing 
suitable clothing are suggested, to keep 
away from common cold. 

2.3.1.2. Influenza 

It was a dreadful disease once and 
worldwide in distribution (pandemic) in 
1970s. 

Causative agent : A(H^NJ Virus , is 




toilet 



Fig. 2.9 HlNl Virus 

spherical in shape and highly contagious, 
causing influenza. 

Symptoms 

Sudden onset of fever accompanied by 
aches and pains in the back and limbs. 

Transmission 

It spreads through nasal and mouth 
droplets of patients and enters into the 
respiratory tract of normal man. It also 
spreads through fomites. 

Prevention 

i. Avoid contact with the patients, 
ii. Avoid crowding. 



^ 



2.3.2. Bacterial diseases 

Bacteria are prokarotic organisms. 
Some of the bacteria are parasitic in 
man, causing diseases like TB, Cholera, 
Typhoid, dysentry etc., 

2.3.2.1. Tuberculosis 

It is an airborne disease affecting the 
lungs and also parts of our body such as 
bones, joints, lymph glands, alimentary 
tract, liver, kidney, etc,. 

Causative agent: Mycobacterium 
tuberculosis, a rod shaped bacterium 
causes tuberculosis (TB). 

Symptoms 

i) The affected parts develop lesions 
in the form of small nodules called 
tubercles from which the disease gets 
its name. 

ii) Persistant cough 

iii) Loss of body weight 
Transmission 

Tuberculosis is transmitted through air. 
Large number of bacteria leave the patients 
through the droplets of sputum expelled 
by the patients while eating, sneezing, 
talking, laughing and so on by the patients. 
The droplets may remain suspended in 
the air for a long time. The dust arising 
from the sputum may also contain 




viable germs. The waxy cell wall of the 
tuberculosis bacillus prevents it from drying 
up and so it can remain viable outside 
the body for a long period. The germs 
suspended in the air may be inhaled by 
a healthy person. 

Prevention 

i) Keeping oneself healthy and avoiding 

insanitary conditions, overcrowding 

and poor ventilation, 
ii) Sunlight and fresh air are important 

agents, as they act as natural 

disinfectants readily destroying the 

germs, 
iii) Isolation of the patients and frequent 

sterilization of articles used by them 

are also important, 
iv) Incineration (burning) of the droplets, 

the sputum from the patients to 

prevent its occurrence in the air. 
v) Immunization with BCG vaccine is 

an effective measure to prevent this 

disease. 



ACTIVITY 2.2 



Making a culture of live bacteria 

Boil a few grams of chopped meat, 
carrot and potatoes in water for 15 
minutes, then filter off the solid matter 
to obtain a fairly clear broth. 

Leave the broth in open test tubes 
for a few hours. Plug the tubes with 
cotton wool and leave them in a warm 
palce (approximately 25°C) until the 
broth has "gone bad" owing to the 
growth of bacteria. 

What you have produced, is a 
bacteria culture. 



Fig. 2.10 Tuberculosis bacteria 



IMMUNE SYSTEM 




Central Nervous - 
System 

Appetite loss 
Fatigue 



Lungs 

Chest Pain 
Coughing up blood 




Prolonged cough 



Skin 



Night sweats, 
Pallor 




I 



Fig. 2.11 Symptoms of tuberculosis 

vi) The patient should cover his mouth 
and nose while coughing. 

2.3.2.2. Typhoid 

Causative agent: A short rod shaped 
bacterium with numerous flagella - 
Salmonella typhi causes typhoid. 

Symptoms 

i) Continuous fever. 

ii) Inflammation and ulceration of 
intestine. 

iii) Enlargement of spleen and a 
characteristic red spot eruption on 
the abdomen. 

Transmission 

Transmission of typhoid is through food 
and water contaminated with the germ, the 
personal contact with patients and carriers. 
Flies are also important transmitting agents 
of this disease. 



Prevention and control: Isolation of 
the patient, control of flies, hygienic food 
habits, proper public sanitary measures 
are effective means of prevention of 
this disease. Artificial immunization with 
typhoid vaccine is advised. A recovery 
from typhoid usually confers a permanent 
immunity. 

2.3.3 Protozoan diseases: 

Some of the unicellular protozoans are 
parasitic pathogens and cause diseases in 
man. 

2.3.3.1 Malaria 

Causative agent: A tiny protozoan - 
Plasmodium is responsible for causing 
malaria. Four different species of 
Plasmodium namely, P.vivax, Pmalariae, 
Pfalciparum and P.ovale occur in India 
causing malaria. Of these, the malignant 
and fatal malaria, caused by Plasmodium 
falciparum is the most serious one. 



Transmission 

Through the vector 
Anopheles mosquito. 



the female 



Symptoms 

i) Malaria is characterized by chillness 
and rise in temperature. This is 
followed by perspiration and lowered 
body temperature. The person feels 
normal for some time but the fever 
recurs at regular intervals. 

ii) Successive attacks of malaria result 
in the distension of spleen and 
destruction of liver tissues. 

Prevention and control: 

i) Sanitary measures include ground 
fogging with disinfectants. 

ii) Closure of stagnant pools of water 
and covering ditches is suggested. 



^ 



Ruptured 
oocyst 




^^^ 



Release of 
sporozoltes 

^Oocyst Sporogonic 
cycle 

Ookinete 



Mosquito blood 
meal: Injects 
sporozoites 




Microgametocyte 

entering 

macrogametocyte Mac^g^etocyte J"ametocytet '^^ 





#^. 



Mosquito blood 
meal: Injects 
gametocytes 



Ruptured/" j^- 
sfchizont IV ^'^ 



Fig. 2.12 Life cycle of malarial parasite 

Life cycle of malarial parasite - Plasmodium: The sexual stage of Plasmodium 
takes place in female Anopheles mosquito whereas the vegetative stage occurs in man. 
When a female Anopheles mosquito bites an infected person, these parasites enter 
the mosquito and undergo further development in the mosquito body. The parasites 
multiply within the body of the mosquito to form sporozoites that are stored in the 
salivary glands of mosquito. When these mosquitoes bite a person, the sporozoites 
(the infectious stage) are introduced into his body; they multiply within the liver cells 
first and enter the RBC of man, resulting in the rupture of RBC. This results in the 
release of toxic substance called haemozoin which is responsible for the chill and high 
fever, recurring three to four days. 



Sir. Ronald Ross 

Sir. Ronald Ross (1857-1932), aBritish- Indian physician was born 
in Almora, India. He had his school education and higher studies 
in medicine in England. Later he was posted at the Presidency 
General Hospital, Calcutta. Ross studied about malaria between 
1882 and 1899. As he was working in Bangalore, he noticed the 
connection between water as breeding ground of mosquitoes 
and the spread of malaria. He discovered the presence of 
malarial parasites in the female Anopheles mosquito when he 
was working on malaria at Secunderabad. He demonstrated that 
malaria is transmitted from infected individual to a healthy person 
by the bite of mosquito. In 1902, he was awarded the Nobel prize 
for his work on malaria. 




IMMUNE SYSTEM 




iii) Using mosquito nets and repellants 
also, will grossly lower the chance 
for infection. 

2.3.3.2.Amoebicdysentry(Amoebiasis) 

Causative agent: Entamoeba 
histolytica - a protozoan parasite in the 
large intestine of man causes Amoebiasis. 

Symptoms 

i) Fever. 

ii) Constipation and abdominal pain and 

cramps, 
iii) Stools with excess mucous and 
blood clot. 
Transmission 

It is a water and food borne disease. 
House flies act as mechanical carrier and 
serve to transmit the parasite from the 
faeces of infected persons to the food - 
thereby contaminating the food and water. 



Six stages of hand washing technique 




1. Palm to Palm 2. Back of Hands 




3. Interdigital spaces 4. Finger Tips 
1 




5. Thumbs and wrists 6. Nails 



Prevention and control: Precaution 
may be taken by providing germ free clean 
water; clean food habits. Good sanitary 
facilities will control the flies. 

2.3.4. Fungal diseases in man 

Some of the fungi are parasitic on man 
and cause diseases 




Fig. 2.13 Clean habits 



Fig. 2.14 Ringworm 

2.3.4.1. Ringworm 

Three different genera of fungi namely, 
Epidermophyton, Microsporum and 
Trichophyton cause ringworm. 

Symptoms 

The above fungi live on the dead cells 
of outer layer of skin in man and cause 
superficial infections in skin, hair, nail, etc; 
and form patches and Itching 

Transmission 

By direct contact or through fomites such 
as towels, combs, etc,. 

Control and prevention: Avoid contact 
with infected person and articles used by 
them. 

2.4. MODES OF TRANSMISSION 



^ 



OF INFECTIOUS GERMS 

The transfer of a disease causing germ 
from an infected person to a normal 
healthy person through certain agents or 
direct contact is called transmission of the 
disease. The transmission can take place 
in one of the following ways; 

Direct Transmission : By direct 
transfer of germs from the patient to normal 
healthy person through close contact, 
the diseases like diphtheria, pneumonia, 
cholera, typhoid, measles, mumps, etc,, 
are transmitted. 

During sneezing, coughing and 
talking, the droplets from the patients are 
discharged from the mouth and the nose 
and enter the air. While a normal person is 
inhaling such air, laden with the droplets. 




Fig. 2.15 Cover face while 

caughiing and sneezing 



he gets infected. 

Through the umblical cord, the germs 
are transferred from the infected mother 
to the child at the time of childbirth by the 
direct contact method. 

Indirect transmission through 
fomites: Some germs may remain viable 
outside the body of the hosts and may 
be transferred indirectly through close 
inanimate objects used by the patients 
like clothing, bedding, handkerchief, 
toilet articles, utensils, drinking cups and 
glasses that are freshly soiled with the 
germs present in the discharges of the 
patients. Such contaminated objects are 
called fomites. 

Transmission by animals: Various 
animals such as ticks, mites, birds, insects 
and mammals transmit diseases like 
cholera, malaria, rabies, etc; 

2,5- IMMUNIZATION 

Immunity: Immunity is part of a complex 
system of defence reaction in the body. It 
means the defence against or specific 
resistance exhibited towards the infectious 
organisms and their products. 

The infectious organisms that invade 
the body and the toxins produced by them 
and any foreign protein entering the body 
are called antigens. 

The immune system which includes 
blood plasma, lymph and lymphocytes 
analyze the chemical nature of the antigens 
and produce the suitable proteinaceous 
substances called antibodies to detoxify 
the antigens. 



IMMUNE SYSTEM 




2.5.1. Types of Immunity 

Natural or Innate Immunity: The 
natural or innate immunity that enables 
an individual to resist the disease, to which 
the particular species is immuned. E.g. 
Plant diseases do not affect animals. 

Acquired or Specific Immunity: 

The resistance against some infectious 
diseases developed by an individual during 
lifetime on exposure to the infections is 
called acquired or specific immunity. 

The acquired or specific immunity is of 
two kinds - active acquired immunity and 
passive acquired immunity. 

Active acquired immunity: This kind 
of immunity is developed by our body, 



during the first infection of any pathogen. 
The antibodies produced in the blood 
stays for a long period and kills the similar 
pathogens whenever they enter the body. 

If the antibody production is stimulated 
naturally, after recovery from a disease, it 
is called Natural Active Acquired Immunity. 

If the antibody synthesis is 
stimulated by application of vaccines or any 
other man made methods, the immunity 
gained is called Artificial Active Acquired 
Immunity. E.g. The polio drops and 
triple antigen injected into the child in the 
immunisation programme. 

Passive Acquired Immunity: In this 
type of immunity, a readymade antibody 
is introduced from outside instead of 



TYPES OF IMMUNITY 



IMMUNITY 



f 



^ 



Natural or Innate 

naturally available right 

from birth 



Acquired or specific 

developed in the body 

after birth 



f 



I — 

Active 

Antibodies are 

produced by 

antigenic stimulus 



i 



Natural 

developed 

after recovering 

from a disease 



— } 

Artificial 
developed by 
immunization 
by introducing 

vaccines 



f 



— } 

Passive 

Pre-formed 

bring forth immunity 

Artificial 



Natural 

through mother's antibodies extracted 
breast milk from other animals 

antibodies of are introduced 

mother enter the child 



^ 



stimulating the body to produce antibody with antigenic stimulus. 

If the readymade antibody is taken from the mother's blood into the foetus, it is called 
Natural Passive Acquired Immunity. If the readymade antibody is given to an individual 
artificially, (produced in some other animal and extracted) it is called Artificial Passive Acquired 



MORE TO KNOW 



What kind of Immunity does a child get when it is breast fed 7BREAST FEED IS THE 
BEST FOOD. Antibodies or Immunoglobins are found in breast milk. Through breast milk 
antibodies are passed on to the nursing baby. Bottle fed infants do not have the advantage 
of fighting the ingested pathogens on their own until the antibodies are produced in them. 
An infant should be breast fed for a minimum of six months. 

Medical establishment knows that infants who are breastfed contract fewer infections than 
bottle fed infants. Breast milk protects the child, against bacteria like Escherichia coli, Sal- 
monella, Shigella, Streptococci, Staphylococci, Pneumococci and viruses like Polioviruses 
and Rotaviruses. 



IMMUNIZATION SCHEDULE 

The immunization schedule indicates the stages at which the vaccinations and 
inoculations have to be given to safeguard children against different diseases. The 
table given below lists the names of vaccines, their dosages and the stage at which 
they have to be administered. 



Immunization sciiedule followed in India ^^^^^^^^^H 


S.No 


Age 


Vaccine 


Dosage 


1 


New born 


BCG 


1^' dose 


2 


1 5 days 


Oral polio 


1 ^* dose 


3 


6"" week 


DPT & Polio 


1 ^* dose 


4 


1 0"^ week 


DPT & Polio 


2"'^ dose 


5 


1 4"^ week 


DPT & Polio 


3'^'=' dose 


6 


9-12 months 


IVIeasles 


1 ®* dose 


7 


18-24 months 


DPT & Polio 


1 ®* booster 


8 


15 months - 2 years 


IVIMR vaccine 


1 ®* dose 


9 


2 — 3 years 


Typhoid vaccine 


2 doses at 1 month gap 


10 


4 — 6 yea's 


DT & Polio 


2"'^ booster 


11 


1 0"' year 


TT & Typhoid 


1 ®' dose 


12 


1 6"^ year 


TT & Typhoid 


2"'^ booster 



IMMUNE SYSTEM 





Fig. 2.16 Oral Polio immunization 

Immunity. This immunity is not permanent. 

Immunization: Administering vaccines to 
prevent the disease is called immunization. 
This process of Immunisation develops 
Artificial Active Acquired Immunity. 

Immunisation through inoculation is a mass 
means of protecting a greater number of 
people against the spread of diseases. 

BCG Tuberculosis Vaccine 

DPT Diphtheria, Pertussis, 

Tetanus Vaccine (Triple antigen) 

MMR Mumps , Measles, Rubella 

DT Diphtheria, Tetanus (Dual antigen) 
Tetanus toxoid 



2,6- TREATMENT AND PREVENTION 
OF THE DISEASES 

Treatment means medical management 
of the symptom of the disease. 

Medical management includes: 

i) Treatment involving medicine. 

ii) reatment not involving medicine. 

Treatment involving medicine: 

Medicines are generally used to treat 
infectious diseases. These medicines 
either reduce the effect of the disease 
or kill the cause of the disease. The 
antibiotics are used as blocks to the 



pathways of the disease without affecting 
ourselves. 

Treatment not involving medicine: 

As a person is recovering from the effect 
of fracture or neurotic problem, yoga and 
physiotherapy do a great deal of help to 
do normal activities. People addicted to 




Fig. 2.17 Yoga practice 

alcohol and drugs are given counselling to 
overcome the habit. 

Prevention: Getting rid of a disease 
causing germs, is a means of prevention of 
the disease. 

Prevention can be achieved in two ways: 

i. General - preventing the infectious 
germs by keeping away from the 
exposure to the germs. Hygienic life 
style, avoiding overcrowding, fresh 
air, safe drinking water and good 
sanitary measures are all ways to 
prevent a disease causing germ, 
coming into contact with us. 

ii. Specific - This relates to a peculiar 
property of the immune system that 
usually fights the microbial infections, 
e.g. Immunisation programme. 

2.7. BIO-TECHNOLOGY IN 
MEDICINE 

A detailed account of the role of 
Biotechnology in healthcare, has been dealt 
with in chapter 1. 



^ 



Biotechnologically synthesized insulin 
has been effectively used replacing the 
defective insulin to treat diabetes mellitus 
in the field of medicine. 

2-8- HIV AND PREVENTION 

Acquired Immune Deficiency 

Syndrome (AIDS) is a dreadful disease 
transmitted through sexual contact or 
through blood and blood products. Robert 
Gallo at National Institute of Health, USA 
and Luc Montagnier at Pasteur Institute, 
Paris isolated the virus. Human Immune 
Deficiency Virus (HIV) which causes 
AIDS. 

HIV is a retro virus with glycoprotein 
envelope and the genetic material - RNA. 
HIV causes profound Immune suppression 
in humans. It is due to the depletion of 
one type of WBC, which is involved in the 
formation of antibodies called CD4 plus 
T-helper cells (lymphocytes). 



Symptoms: Significant weight 
loss, chronic diarrhoea, prolonged 
fever, opportunistic infections such as 
tuberculosis, candidiasis and recurrent 
herpes zoster (viral) infection. 

Test for Virus: 

1. Enzyme Linked Immune Sorbent 
Assay (ELISA) 

2. Western Blot - a confirmatory test. 
Prevention: 

1. Protected sexual behaviour. 

2. Safe sex practices. 

3. Screening the blood for HIV before 
blood transfusion. 

4. Usage of disposable syringes in the 
hospitals. 

5. Not sharing the razors / blades in the 
saloon. 

6. Avoid tattooing using common needle. 



EVALUATION 



PART A 

1 



Pick out a case of healthy state of an 
individual. 

Mr. X is recovering from an infectious 
disease, 

Mr. Y is taking insulin injection 
everyday, 

Mrs. Z is very much depressed, 

Mr. K is attending to his duty and 
spends time joyfully. 



2. Which one of the following is a state 
of a disease in which a person is not 
socially balanced. 

He enjoys a birthday party. 

He behaves rudely even for menial 
matters. 

He is adjusting to the surrounding 
situation. 

He is attending to his ailing mother 
at the hospital. 



IMMUNE SYSTEM 




3. Pick out the bacterial disease. 
Meningitis, Rabies,Tetanus, Small pox. 

4. One of the following is transmitted 
through air. Find out. 

Tuberculosis, Meningitis,Typhoid, 
Cholera. 

5. The most serious form of malaria is 
caused by Plasmodium . 

P.ovale, Pmalariae, P.falciparum, 
Pvivax. 

6. An example for protozoan infecting our 
intestine is . 

Plasmodium vivax. Entamoeba 
histolytica,Trypanosomagambiense, 
Taenia solium. 

7. One of the means of indirect 
transmission of a disease is . 

Sneezing, Droplet from mouth. 

Placenta, Utensils of patients. 

8. When antibodies, extracted from some 
other animal is injected into your body, 
what kind of immunity do you gain? 

Artificial active acquired immunity, 

Artificial passive acquired immunity, 

Natural active acquired immunity. 

Natural passive acquired immunity. 

9. The first vaccine injected into a just 
born baby is . 

Oral polio, DPT, 

DPT and Oral polio,BCG. 

10. Pick out a non-antigen. Entry of 



PART B 

11. In order to lead a healthy life a 
person should enjoy physical, 
mental and social well being 
If a person lacks any one of them, 
then that person is suffering from 



12. Tamil selvan has inherited colour 
blindness from his father. Name the 
causative factor responsible for this 
defect . 

13. Marasmus and Kwashiorkar are both 
protein deficiency defects. Marasmus 
differs from Kwashiorkar in enlarged 
belly and swelling in the face. Are these 
symptoms forthe above diseases correct? 
If not, correct it. 

14. A list of disorders are given below. Pick 
out the odd one out and give reasons, 
(colour blindness, haemophilia, 
night blindness, albinism, sickle cell 
anaemia) 

15. Ramya is suffering from bleeding gum 
and loosening teeth. On a diagnosis, 
it was found to have been caused by 
vitamin deficiency. 

Suggest Ramya the kind of vitamin that 
is lacking in her food and tell your friend 
the name of deficiency disease that she 
suffers from. 

(A) Vitamins 

(B) Deficiency diseases and 

(C) Symptoms are given. 



(Germ,Toxins of germs, New forms of ^, ^ . o ^ ^.u a 
. ■ \a .1. > ^>ln Match B,C with A. 

protein. Mother s Milk. 



-^ 



A 


B 


C _ 


Vitamins 


Deficiency diseases 


Symptoms 


e.g. Vitamin A 


Nyctalopia 


Niglit Blindness 


Vitamin Bl 


Scurvy 


Nerbvous disorder 


Vitamin C 


Ricl<ets 


Bleeding Gum 


Vitamin D 


Haemorrliage 


Defective calcification 
of bones 


Vitamin K 


Beri-beri 


Profuse loss of blood 



16. Kavitha is suffering from common cold. What are the questions you will 



put forth to Kavitha to confirm the 
disease? 



a. 
b. 



PART C 

17. Kala has delivered a baby, 

a. Suggest the immunization schedule 
for the baby, in the first six months 

b. What are all the diseases that can 
be cured as per the schedule? 



18. There is a widespread outbreak of 
malaria in your area. 

a. Suggest some controlling 
measures to the local authorities 
concerned. 

b. Pick out the right symptom for 
malaria, (chill and shiver and a rise 
in temperature / diarrhoea ) 

19. 15th October is observed as 
'Handwashing Day' 

a. Tell your friend the effects of hand 
washing. 

b. In a day what are the occasions in 
which you wash your hand? 



FURTHER REFERENCE 

Books: 1. Biology - RAVEN, Johnson WCB Mc Graw - Hill 

2. Biology -A Modern Introduction, B.S. Beckett, Second Edition Oxform 
University Press. 



Chapter 





STRUCTURE AND FUNCTIONS 

r, OF HUMAN BODY-ORGAN 
' SYSTEMS 




3. STRUCTURE AND FUNCTIONS OF 
HUMAN BODY-ORGAN SYSTEMS 



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NERVOUS SYSTEM - 
INTRODUCTION 

Two or more people when gather to- 
gether, each one is set with an interest 
and aptitude and performs his works in 
his own way. But when it is the question 
of maintenance of an order, a systematic 
working among them, there is a need for 
someone to control and co-ordinate them 
so that a harmony prevails. Similarly the 
functions of organs and organ system is 
our body cannot go on in their own way 
but must be coordinated to maintain the 
harmonius steady state of body function- 
ing called Homeostasis. Coordination is 
the process through which two or more 
organs interact and compliment the func- 
tions of one or the other. In our body the 
neural or nervous system and the endo- 
crine system do the function of coordinat- 
ing and integrating all the activities of the 
organs so that the body works efficiently 
by synchronizing the functions. 

The nervous system provides an organ- 
ized network of point to point connections 
for a quicker coordination. The endocrine 
system provides chemical integration 



through hormones. In this chapter, we will 
learn the structure and functioning of the 
nervous system and the endocrine sys- 
tem in man. 



Dendrite 



NissI granule 

■ Nucleus 

Cell body 

Nodes of Ranvier 




Cytoplasm 



Terminal 
ches 



Nurilemma 



Axon 
Myelin sheath 

Neuron 




Dendrite 



Mucleus 



,, . , Bipolar 

Unipolar ^ Multipolar 

Fig. 3.1 structure of neuron and types 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




3-1 NERVOUS SYSTEM 

The nervous system of an animal is 
composed of 

i) Specialized cells called neurons 
or nerve cells which can detect, 
receive and transmit different kinds 
of stimuli. 

ii) The nerve fibres which are certain 
bundles of extended processes of 
nerve cells. 

3.1.1 Nerve cells 

Nerve cells or neurons are the 
structural and functional units of the 
nervous system. 

Billions of nerve cells make up our brain. 
A nerve cell is a microscopic structure 
consisting of three major parts namely 
cell body, dendrites and axon. 

Cell body 

It is the cell structure irregular in 
shape or polyhedral structure, it is also 
called as cyton. Cell body contains 
cytoplasm with typical cell organelles 
and certain granular bodies are called 
NissI granules . 

Dendrites 

Dendrites or Dendrons are shorter 
fibres which branch repeatedly and 
project out of the cell body. Dendrites 
transmit electrical impulses towards the 
cyton. 

Axon 

One of the fibres arising from the cell 
body is very long with a branched distal 
end and it is called as Axon. 



The distal branches terminate as 
bulb like structures called synaptic 
knob filled with chemicals called neuro 
transmitters. Axon contains axoplasm 
inside and is covered by a membrane 
called neurilemma. Neurilemma en- 
closes the axon except at the branched 
distal ends. In some neurons called 
myelinated neurons an additional white 
fatty fibre called myelin sheath covers 
the neurilemma. Myelin sheath is not 
continous over the neurilemma. The 
gaps left by the myelin sheath on the 
axon are called Nodes of Ranvier. Over 
the myelin sheath are found certain 
cells called Schwann cells. 

Types of nerve cells 

a) Myelinated or Medullated or White 
neurons: 

When the axon is enclosed by the 
white fatty myelin cover it is called My- 
elinated or Medullated or White neu- 
rons. This forms the cerebral cortex of 
our brain. 

b) Non- Myelinated or Non-Medullated or 
Grey neurons: 

This neuron is not enclosed by myelin 
sheath; so it appears greyish in colour. 
The axon is covered by only neuri- 
lemma and Schwann cells. This type 
of neuron is found in the white matter 
of cerebrum. 

c) Unipolar neurons: 

The embryonic nervous tissue con- 
tains unipolar neurons. An unipolar 
neuron has a nerve cell body with a 
single process or fibre, which will act 
both as axon and Dendron. 



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d) Bipolar neurons: 

The sensory hair cells of the sense 
organs like rods and cones of retina 
are made up of bipolar neurons. Each 
bipolar neuron has a cell body and two 
process at the ends, one acting as 
axon and the other acting as Dendron. 

e) Multipolar neuron: 

The cerebral cortex contains the 
multipolar neurons; each multipolar 
neuron has a cell body with many 
dendrites and an axon. 

Synapse: The dendrites and the synaptic 
knobs of the axons of neighbouring 



ACTIVITY 3.1 



Visit a hospital in your locality and study 
the principle behind the administration 
of anesthesia at the time of surgery. 
Find out if the fat soluble anesthetic 
substances like chloroform, ether etc,, 
merge with medullary sheath and 
prevent conduction of nerve impulse. 



k 



S 



neurons are in physical contact with 
one another without fusing. This point of 
contact between the neighbouring nerve 
cells is called synapse. 

3.1.2 Nerve impulse: 

The conduction of stimuli by the 
nerve cells is called nerve impulse. The 
dendrites will receive the stimuli from 
the receptor (sense organ) and conduct 
the same as electrical impulse to the 
axon through the cyton. At the synapse, 
the synaptic knobs release out chemical 
substances called neuro transmitters 



which convert the electrical impulse 
into chemical impulse and pass it to the 
neighbouring neuron. 

3.1-3 Human nervous system 

The human nervous system is divided into 

a) The Central Nervous System 
(CNS) and 

b) The Peripheral Nervous System 
(PNS) 

c) The Autonomic Nervous System 
(ANS) 

The CNS includes the brain and spinal 
cord and it is the site of information 
processing and control. 

The PNS comprises of the nerves of the 
body associated with the central nervous 
system. 

3.1.3.1 Central Nervous System 

It is organized of two organs namely 
the brain and the spinal cord. The CNS 
is accommodated in the protective bony 
structures namely skull and vertebral 
column. 

MENINGES: The central nervous 
system is covered by three protective 
coverings or envelops collectively 
called meninges. The outermost cover 
lying below the skull and vertebral 
column is doubly thick and is called 
Duramater. The middle covering is 
thin and vascularised and is called 
Arachnoid membrane. The innermost 
cover is a very thin delicate membrane 
and is closely applied on the outer 
surface of brain and spinal cord and it 
is called Piamater. 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




3.1.3.1-1 The Brain 

Man is a vertebrate and a mammal 
belonging to the animal kingdom. But, 
he stands unique and supreme and this 
supremacy in the living world is reflected 



Cerebellum 
Spinal 



Cerebrum 



— Cervical nerves 



—Thoracic nerves 




■Tibial nerve 



in the organization of the brain. The brain 
is the central information processing 
organ and acts as the command and 
control system. 

The human brain as in the case of other 
vertebrates, is divided into three major 
parts: 



a) Fore brain 
c) Hind brain 
Fore brain 



b) Mid brain 



Fore brain consists of 
thalamus and hypothalamus. 

Cerebrum 



cerebrum. 



Fig. 2.2 Human Nervous System 



This forms the major part of the human 
brain (nearly two third of the brain is 
cerebrum). A deep cleft called median 
cleft divides the cerebrum longitudinally 
into two halves as right and left cerebral 
hemispheres, which are united at the 
base by a sheet of nervous tissue called 
corpus caiiosum, The outer region of 
the cerebrum is distinguished as, the grey 
matter or cerebral cortex and the inner 
region is called white matter. 

Cerebral cortex 

It consists of the nerve cell bodies of 
several layers of greyish nerve cells giving 
grey colour - so called as grey matter. The 
increased surface area of the cerebral 
cortex in man is folded and thrown into 
a pattern of convolutions consisting of 
ridges and furrows. 

Cerebral cortex contains 

a) motor areas 

b) sensory areas and 

c) association areas (a region that is 
neither sensory nor motor). 



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Motor areas 

Motor areas are the sites of order or 
command of the cerebrum, from where 
the order arises to control the activities 
of the different organs of our body. 
Initiation of voluntary activities takes 
place here. 



Major Internal Parts of the Human Brain 

Cingulate 
sulcus 



Corpus 
callosum" 
Midbrain 



Temporal 
lobe 




Cerebellum 



Fig. 3.3 Major internal parts of liuman brain. 

Sensory areas 

These are the sites where the sensory 
functions of the various sense organs are 
received through the sensory nerves. 

Association areas 

These are responsible for complex 
functions like intersensory associations, 
memory and communication. 

White matter of cerebrum: The inner 
part of the cerebrum lying below the 
cerebral cortex is called white matter 
and it consists of bundles of nerve 
fibres with myelin sheath giving the 
white colour. Some of these bundles of 
nerve fibres connect the different parts 
of the cerebrum while others connect the 
cerebrum with the rest of the brain and 
spinal cord. 



Within the cerebral hemispheres are 
present cavities called ventricles, filled 
with a nutritive fluid called cerebro spinal 
fluid. 

Functions of cerebrum: Cerebrum is 
the seat of consciousness, intelligence, 
memory, imagination and reasoning. It 
receives impulses from different parts 
of the body and initiates voluntary 
activities. Specific areas of cerebrum 
are associated with specific functions. 
Thus there is a centre for hearing, 
another for seeing, another for tasting, 
another for smelling, another for 
speaking and so on. A damage in 
a specific centre of cerebrum will 
deprive the particular faculty from doing 
its functions. 

Thalamus 

Cerebrum wraps around a structure 
called thalamus - a major conducting 
centre for sensory and motor signalling. 

Hypothalamus 

It lies at the base of the thalamus. 
It controls body temperature, urge to 



Speech 



Motor control 




■Touch and 
Pressure 



Taste 
Hearing 

Language 

Reading 

Vision 



Smell 



Fig. 3.4 Functional areas of human brain. 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




eat and drink, regulation of sexual 
behaviour, express emotional reactions 
like excitement, anger, fear, pleasure 
and motivation. 

Mid brain 

The mid brain is located between the 
thalamus and the hind brain. A canal 
called cerebral aqueduct passes through 
the mid brain. The dorsal portion of the 
mid brain consists of four hemispherical 
bodies called corpora quadrigemina 
which controls and regulates the various 
visual reflexes and optical orientation. 

Mid brain with hind brain together form 
the brain stem. 

Hind brain 

Hind brain comprises of pons, 
cerebellum and medulla oblongata. 

Cerebellum 

It lies below the cerebrum and consists 
of a median portion and two lateral lobes. 
Cerebellum regulates and coordinates the 
group movements of voluntary muscles 
as in walking or running. 

Pons 

It is the bridge of nerve fibres that 
connects the lobes of cerebellum. It relays 
the information from the cerebrum to 
cerebellum. It also contains sleep centre 
and respiratory centre. 

Medulla oblongata 

Medulla is the posterior most part of the 
brain where it merges with the spinal cord. 
It acts as a coordination pathway for both 
ascending and descending nerve tracts. 
Medulla is the centre for several reflexes 



involved in the regulation of heartbeat, 
blood vessel contraction, breathing, etc,. 

The ventricle of the medulla remains 
connected with the ventricles of the 
cerebral hemisphere. 

3.1.3.1.2 The Spinal cord 

This is atubular structure, acontinuation 
of the brain lying in the neural canal of the 
vertebral column. The three meninges - 
Piamater, Arachnoid membrane and the 
Duramater cover the spinal cord as in the 
case of brain. 

The spinal cord has two enlargements 
- one in the neck region of the body 
called cervical plexus and another in 
the lumbar region of the vertebral column 
called lumbar plexus. 

The spinal nerves arise from these 
enlargements. The lower end of the 
spinal cord is filamentous and is called 
Filum terminale. On the mid dorsal 
side of the spinal cord is found a narrow 
depression called dorsal fissure and on 
the mid ventral side of the spinal cord is 
found a deep depression called ventral 
fissure. Running through the center 
of the spinal cord is the central canal, 
an extension of the ventricle filled with 
cerebro spinal fluid. Outer region of the 
spinal cord contains medullated white 
neurons and the inner region contains 
non-medullated grey neurons. The spinal 
cord conducts impulses to and from the 
brain and acts as a reflex centre. 

3.1.3.2 Peripheral nervous system 
(PNS) 

The nerves arising from the brain and 
spinal cord constitute the PNS. 



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a) Cranial nerves: 

Twelve pairs of cranial nerves arise 
from the brain. Some of the cranial 
nerves are sensory nerves (taking 
impulse from the sense organ to the 
brain e.g., optic nerves from the eyes). 
Some of the cranial nerves are the 
motor nerves taking impulse from the 
brain to the effector organ, e.g. vagus 
nerve innervating the heart and some 
are mixed nerves with both sensory 
and motor functions, e.g facial nerve 

b) Spinal nerves: 

Thirty one pairs of spinal nerves arise 
from the spinal cord. Each spinal nerve 
has a sensory root and a motor root. 
Thus, all spinal nerves are mixed nerves. 

3.1.3.3 The Autonomic Nervous 
System (ANS) 

Itcontrolsthefunctionsofthe vital organs 
of the body through its two antagonistic 
divisions namely, sympathetic nerves and 
parasympathetic nerves. 



3,2, ENDOCRINE 
MAN 



SYSTEM IN 



The chemical coordination of 
physiological processes to maintain the 
homeostasis is the work of endocrine 
system. Endocrines control and coordinate 
the physical processes of growth, 
reproduction and sustenance of life. 

Endocrine system consists of a number 
of endocrine glands and their hormones. 

Endocrine glands are ductless glands 
(without ducts), secreting the chemical 
substances called hormones. The 



hormones are carried by the blood from 
the site of production to the site of action. 

Endocrine glands in man are distributed 
in the different regions of the body without 
interconnections. The various endocrine 
glands found in different regions in man 
are as follows: 



Hypothalamus 

Pineal 
Pituitary 

Thyroid and 
parathyroid 

Thymus 



Pancreas 
Adrenal 

Ovary 
(In femalef 



Testis 
(In male) 




Fig. 3.5 Endocrine system in man 



Head 


- a) pituitary gland 




b) pineal gland 


Neck 


- a) thyroid gland 




b) parathyroid gland 


Thorax 


- thymus gland 


Abdomen - 


- a) pancreas - Islets of 




Langerhans 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




b) adrenal glands - 
adrenal cortex and 
adrenal medulla 

c) gonads - testes in man 
and ovaries in woman 



Hormones 



Chemically hormones are proteins 
or amino acids or steroids. Though the 
hormones are secreted in small quantities, 
their performance is profound in action. 

Pituitary gland 

It is a tiny gland of the size of a pea 
attached to the hypothalamus of the brain. 
Since some of the endocrine glands are 
regulated by the pituitary gland, it is called 
as the conductor of endocrine orchestra. 

Divisions of pituitary : Pituitary gland 
is differentiated into an anterior lobe called 
adenohypophysis and a posterior lobe 
called neurohypophysis. 



Adenohypophsis 

(Anterior Pituitary) 




Infundibular 
stalk 



eurohypophsis 

(Posterior Pituitary) 



Fig. 3.6 Diagrammatic internal 
view of pituitary gland 



s 



Hormones of 
adenohypophysis 



Somatotropic or 

Growth hormone 

(STH or GH) 



Thyrotropic or Thyroid 
stimulating hormone (TSH) 



Adrenocorticotropic 
or Adrenal cortex 
stimulating hormone (ACTH) 



QrTctions and malfunctions 



It brings forth growth in general 

Less production in children - dwarfism 
with retarded growth 

Excess production in children -g/ganf/s/i? 
with excess growth 

Excess production in adolescents - 
acromega/y with large limbs and lower jaw 



It stimulates the growth of thyroid gland and 
its production - the thyroxine 



It stimulates the adrenalcortex to produce the 
hormones aldosterone and cortisone 




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Follicle stimulating 
hormone (FSH) 


It stimulates the maturation of graafian follicles (in 
the ovary) in the female, to produce the eggs and 
sperm formation in the males. 


Lutenizing hormone (LH) 
in female 

or interstitial cell 
stimulating hormone 
(ICSH) in male 


LH in female causes discharge of egg from graafian 
follicle - a process, called ovulation and production 
of female sex hormone oestrogen and progesterone. 

ICSH in male, induces the interstitial cells to produce 
male sex hormone - testosterone 


Lactogenic hormone 
(LTH) 


It stimulates the growth of mammary glands in 
female and milk production after child birth. 



u 



The hormones of neuro 

hypophysis namely, oxytocin 

and vasopressin are secreted 

by hypothalamus and are 

released on specific stimuli. 

Thus the neurohypophysis 

hormones are secretions of a 

part of the nervous system and 

are chemically octapetides and 

decapetides 



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Hormones of Ney 
hypophysis | 


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^^^^ Functions and malfunctions ^^^^| 


Oxytocin 


It speeds up the child birth process, by stimulating the 
contraction and relaxation of the uterus in the female. 


Vasopressin 

or Antidiuretic 

hormone (ADH) 


It helps in the reabsorption of water, producing 
concentrated urine in small quantity. 

It constricts the blood vessels and raises up the blood 
pressure 

Less production of ADH results in diabetes insipidus, 
leading to production of excess of dilute urine. 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




Thyroid gland 

The bilobed thyroid gland is located 
in the neck, one lobe on each side of 



Vocal cord 





Parathyroid 



Fig. 3. 7 Thyroid gland a) Dorsal view 
b) Ventral view 

larynx, which secretes a hormone called 
thyroxine. Thyroxine is an iodinated 
protein, composed of the amino acid, 
tyrosine and iodine. 



Functions of thyroxine 

• It increases the rate of metabolism. 

• It stimulates a rise in the body 
temperature. 

• It promotes growth and differentiation 
of tissues. 

• Since it affects indirectly growth of 
the body, thyroxine is also called as 
personality hormone. 

• it regulates iodine and sugar level in 
the blood. 

• it controls working of kidneys and 
urine output. 

Thyroid disorders 

1) Hypothyroidism - less secretion 
of thyroxine causes many 
abnormalities, like simple goitre, 
myxoedema and cretinism. 

a) Simple goiter - It is due to the 
deficiency of iodine in our diet. 
Thyroid gland bulges as a swelling 
in the neck and it is called as goiter. 

b) Myxoedema - It is caused in the 
adults, the symptoms are, low 




Fig. 3.8 a person with goitre 



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metabolic rate, loss of mental 
and physical vigour, increase in 
weight, thickening of skin, lowered 
heartbeat, mental dullness, etc,. 

c) Cretinism - This is produced in 
children and the symptoms are 
stunted growth, retarded mental 
development, defective teeth, 
protrusion of tongue and loose skin. 

2) Hyperthyroidism - The excess 
production of thyroxine causes 
exophthalmic goiter or Grave's 
disease. The symptoms are high 
metabolic rate, high blood pressure, 
high irritability, profuse sweating, loss 
of weight, fatigueness and protrusion 
of eyeballs. 

The islets of Langerhans 

Pancreas is a dual role playing 
endocrine gland. The exocrine parts 
produce pancreatic juice. The endocrine 
portion is called islets of Langerhans. It 
consists of two type of cells namely, alpha 



Duodenum 




Pancreatic 



Group of cells 
forming islets of 

langerhans 
(Endocrine part) 



Fig. 3.9 Pancreas showing 
islets of Langerhans 



cells and beta cells. Alpha cells produce 
a hormone called glucagon and Beta 
cells produce insulin and amylin. 

Insulin 

• It promotes the uptake of glucose by 
the cells for tissue oxidation. 

• It favours conversion of glucose, 
into glycogen and its storage in the 
liver and the muscles. 

• It prevents the formation of glucose 
from protein and fat. 

• It maintains normal blood glucose 
level at 80 - 120 mg / 100 ml of 
blood. 

Diabetes mellitus 

Less production of insulin causes 
Diabetes mellitus, in which the excess 
unused glucose is excreted in the urine. 

Glucagon 

• It is secreted when glucose level in 
the blood is low. 

• It influences conversion of glycogen 
into glucose, thus raising the blood 
glucose level. 



Adrenal gland 



Adrenal cortex 




Kidney 



Adrenal medulla 



Fig. 3.10 a) Adrenal gland 

b) LS of Adrenal gland 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




Adrenal gland (Supra renal gland) 

On each kidney is found an adrenal 
gland. It is composed of two portions, an 
outer adrenal cortex and an inner adrenal 
medulla. 

Adrenal cortex 

It secretes two hormones namely, 
Aldosterone and Cortisone 

Aldosterone (Mineralocorticoid) 

It maintains mineral metabolism, by 
favouring reabsorption of sodium and 
water and excretion of potassium and 
phosphate ions. 

It maintains electrolyte balance, body 
fluid volume, osmotic pressure and blood 
pressure. 

Cortisone (glucocorticoid) 

It stimulates the breakdown of glycogen 
into glucose raising the blood glucose, 
level. 

It also produces an anti-inflammatory 
reaction and suppresses the immune 
response. 

Adrenal medulla 

It is made up of modified 
neuroectodermal cells. It secretes 
two hormones, namely adrenaline 
(epinephrine) and noradrenaline 
(norepinephrine). They are together 
called emergency hormones or 
hormones of flight and fight as they 
rapidly mobilize the body to face a stress 
or emergency situation. 

• They increase the heartbeat. 

• They increase alertness. 



They increase the respiratory rate. 

They promote the conversion of 
glycogen into glucose. 

They cause dilation of pupil. 

They cause profuse sweating. 

They make the hair stand erect, 
(gooseflesh) 

In short noradrenaline and adrenaline 
mobilize the body, to face the 
emergency by fighting with it or running 
away from it. 



Testes 

They are both cytogenic (producing 
sex cells) and endocrine (producing male 
sex hormones) in functioning. 

The endocrine part secretes male sex 
hormone called testosterones (androgen). 

Testosterone stimulates the growth of 
reproductive organs and the production 
of male sex cell, the sperms. 

Testosterone determines the 
secondary sexual characters in male, 
such as growth of facial hairs, hoarse 
voice, broadening of shoulder, etc,. 

Ovaries 

Ovaries are both cytogenic (producing 
egg cells) and endocrine (producing 
reproductive hormones, such as 
oestrogen, progesterone and relaxin) in 
functioning. 

Oestrogen is responsible for growth 
of female reproductive organs and the 
appearance of secondary sexual characters 
in female, such as growth of pubic hairs, 
soft voice, feminine body, etc.. 



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Progesterone maintains pregnancy and 
regulates menstrual cycle. 

Relaxin relaxes the muscles of the 
pelvic region at the time of child birth. 

Parathyroid gland 

These are found within thyroid 
and produce the hormones mainly 
parathormone and calcitonin which 
maintain the mineral metabolism. 

Thymus gland 

It's a lymphoid mass, present 
above the heart. It secretes thymosin 
which stimulates the differentiation of 
"T"lymphocytes to resist infection. 

Pineal gland 

It lies under the corpus callosum in the 
brain. It produces melatonin .causing 
concentration of pigments in some specific 
areas like areola, scrotal sacs, etc,. 

3-3- CELL DIVISION 

A matured cell divides into two 
daughter cells. Unicellular animalcules 
like amoeba, undergo binary fission - 
without any change in the chromatin 
reticulum by a type of cell division called 
Amitosis. 

Body cells of all animals and plants 
undergo a cell division called l\/litosis 
, involving changes in the structure of 
chromosomes, but without any change 
in the chromosomal number. 



You have studied the process of mitosis 
in the previous year. We will understand 
the various stages of meiosis and its 
significance in this unit. 



MEIOSIS 



Chromosome 
replication 



Paternal 
homologue 

Maternal 
homologue 



Pairing of 

homologous 

chromosomes 



Synapsis and 
crossing over 




Fig. 3.11 Meiosis - stages 



Meiosis 



The germinal epithelial cells of Meiosis is a kind of cell division, which 

animals undergo l\/leiosis cell division, occurs in the germinal epithelial cells 

involving changes in the structure and of the gonads to form the gametes, 

number of chromosomes. Meiosis takes place in the specialized 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




diploid cells of gonads and produces 
four haploid gametes, each having 
half the number of chromosomes as 
compared to the parent cell. Meiosis 
is completed in two successive 
divisions - Meiosis-I and Meiosis-ll. 
In Meiosis-I, as the chromosomal number 
is reduced to half, it is called Reduction 
division. Meiosis-ll is similar to Mitosis. 

Meiosis - 1 

The various events of Meiosis-I are 
studied under four substages namely 
Prophase-I, Metaphase-I, Anaphase-I and 
Telophase-I. 

Prophase - 1 

The chromatin reticulum unwebs and 
individual chromosomes are liberated 
from one another. The nuclear membrane 
dissolves. The chromosomes undergo, 
marked differences in their shape and 
structure. Based on the shape of the 
chromosomes, this stage is studied under 
five sub-divisions as Leptotene, Zygotene, 
Pachytene, Diplotene and Diakinesis. 

Leptotene 

The chromosomes condense and appear 
like threads. Each chromosome splits up 
longitudinally, except at the centromere. 

Zygotene 

The homologous chromosomes come 
closer and start pairing, (a homologous 
pair of chromosomes consist of a paternal 
chromosome and maternal chromosome 
with similar genes). The pairing starts from 
the tip or from the middle and get attached 
laterally throughout the length. This pairing is 
called Synapsis, the paired chromosomes 
are called Bivalents. 



Pachytene 

The paired chromosomes become 
shorter and thicker. Each bivalent 
appears to have four strands called as, 
tetrads or quadrivalents. The point 
of contact between the homologous 
pair of chromosomes are called, 
Chiasmata. At the point of chiasmata, 
exchange of chromosomal segment 
takes place, between the chromatids of 
the homologous pairs. This exchange 
of segments of chromatids between 
homologous chromosomes, is called 
crossing over. 

Diplotene 

After the crossing over is completed, the 
homologous chromosomes separate and 
this separation is called terminalization. 
Terminalization may begin in chiasmata 
and move to the terminal end of the 
chromosomes. 

Diakinesis 

The nuclear membrane and the 
nucleolus disappear. The spindle 
apparatus is formed in the cytoplasm. 

Metaphase - 1 

The chromosomes get condensed. 
Bivalents now appear on the equator of 
the spindle with their chromatids, pointing 
towards the equatorial plate and the 
centromere pointing towards the poles. 

Anaphase - 1 

The spindle fibres contract pulling the 
chromosomes, towards the opposite poles. 
The entire chromosome, with the two 
chromatids move to the opposite poles. 
This involves, a reduction in the number 



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of chromosomes. Now two groups of 
chromosomes are produced, one at each 
pole with half the number of chromosomes. 

Telophase - 1 

At the poles, around the group of 
chromosomes, a nuclear membrane 
develops. Thus two daughter nuclei each 
with half the number of chromosomes, 
are formed at the poles. The spindle 
fibres disappear. 

At the end of Meiosis-I at right angle to 
the position of the nuclei, the cytoplasmic 
constriction takes place leading to the 
division of the cell. The cytoplasmic 
division is called Cytokinesis. 

Meiosis - II 

Meiosis-ll is similar to Mitosis and so 
it is called Meiotic Mitosis. The events 
of Meiosis-ll are studied in four sub-divi- 
sions as, Prophase-ll, Metaphase-ll, Ana- 
phase-ll and Telophase-ll. 

Prophase - II 

The bivalent chromosomes gets 
shortened. The centrioles form asters 
and move to the poles. The nucleolus and 
nuclear membrane disappear. 

Metaphase - II 

Chromosomes, each consisting of two 
chromatids held together by a centromere 
are arranged at the equator of the spindle 
fibres. The centromeres are attached with 
the spindle fibres. 

Anaphase - II 

The centromere divides into two and the 
two chromatids separate and now they are 
called as daughter chromosomes or new 



chromosomes. The daughter chromosomes 
move towards the opposite poles. 

Telophase - II 

The haploid set at the two poles coil 
to form chromatin material. The nuclear 
membrane and nucleolus reappear. Thus 
two daughter nuclei are formed. 

Cytokinesis 

The cytoplasmic division takes place 
at right angles to the position of the nuclei 
resulting in the formation of four gametes. 

Significance of Meiosis 

1. Haploid sex cells are produced, in 
order to maintain the constancy in the 
number of chromosomes of a species. 

2. Crossing over results in variation of 
genetic traits in the offspring. 

3. Variations form the raw material for 
evolution. 

3-4, HEREDITY 

The resemblance of son or daugh- 
ter with his or her father or mother, is an 
interesting feature in nature. Inheritance 
of characters from the parents to the 
progeny, (i.e heredity) ensures the passing 
of the parental characters to the progeny. 
The inheritance of characteristics through 
generations is called heredity. 

The inheritable characters may be 
morphological or physiological or anatomical 
or reproductive and are also known as traits. 
Both the mother and father contribute equal 
amount of genetic material to the child. This 
means, that each trait can be influenced, by 
both paternal and maternal genetic material 
i.e DNA. 



STRUCTURE AND FUNCTIONS OF HUMAN BODY 




EVALUATION 



Part A 

1. Unipolar neurons are found in 



Brain, Spinal Chord, Embryonic 
nervous tissue. Adult nervous 
tissue. 

2. The sensory organs contain 



Unipolar neuron, Bipolar neuron. 
Multipolar neuron, Medullated neuron. 

3. The part of brain which controls 
emotional reactions in our body is 



Cerebellum, Cerebrum, Thalamus, 
Hypothalamus. 

4. One of the following is the part of the 
brain stem. Pick out. 

Fore brain and mid brain. Mid brain 
and hind brain. 

Fore brain and hind brain. Fore 
brain and spinal cord. 

5. Spinal nerves are . 



Sensory nerves. Motor nerves. 
Mixed nerves. Innervating the brain. 

6. An endocrine gland found in neck is 



adrenal gland, pituitary gland, 
thyroid gland, pancreas. 

7. An endocrine gland which is both 
exocrine and endocrine is . 

(pancreas, pituitary, thyroid, adrenal). 



8. Normal blood glucose level in 100 miof 
blood is . 

9. The "T" lymphocytes are differentiated 

to resist infection in . (parathyroid 

gland, lymph gland,thymus gland, 
adrenal gland). 

10. In Meiosis-I, the pairing of homologous 
chromosomes take place during 

stage, (leptotene, zygotene, 

pachytene, diplotene) 

Parte 

11. Copy the diagram and label any two 
parts in the group given. 




(cyton, axon, dendron, endplate) 

12. This diagram is human brain, and the 
functions of different parts are given 
below. 



A. Seat of smell 

B. Seat of vision 



Mark A and B in the parts of the brain. 
Corresponding with the function. 

13. On the basis ofthe function performed. 
Pick out the right statements, 
a. Pitutiary gland secretes hormones 
and enzymes 

b. Thyroid gland secretes thyroxine 
and insulin. 




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c. Testes produces sperms and the 
hormone androgen. 

d. Pancreas produces enzymes and 
harmones. 

14.Based on relationships fill in the blanks. 

Thyroxine: personality hormone; 
adrenaline : 



17. In Amoeba, the cell division takes 
place 



15. Correct the statements if they are 
wrong. 

a .alpha cells produce insulin and 
beta cells produce glucagon 

b. cortisone suppresses the immune 
response 

c. thymus gland is a lymphoid mass. 

d. Ovary produces eggs and 
Androgen.. 

16. Reduction division is the process by 
which gametes are produced,. The 
cells in which reduction division take 
place are 

(germinal epithelial cells, the sensory 
epithelial cells, cuboidal epithelial 
cells, columnar epithelial cells.) 



(involving changes 
chromatinreticulum. 



in 



the 



without involving changes in the 
chromatin reticulum, 

leading to reduction in the number 
of chromosomes, without dividing 
the nucleus. ) 

18. Pick out the item which has sequential 
arrangements 

a. zygotene -> Leptotene -> Pachytene 
-> Diplotene -> Diakinesis 

b. Diakinesis -> zygotene -> Leptotene 
-> Pachytene -> Diplotene 

c. Leptotene -> zygotene -> Pachytene 
-> Diplotene -> Diakinesis 

19. The important event of meiosis is the 
crossing over. It occurs during 

(Leptotene, Pachytene, Diplotene, 
Zygotene. ) 



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FURTHER REFERENCE 

Books: 1. Biology - RAVEN, Johnson WCB Mc Graw - Hill 

2. Biology - A Modern Introduction, B.S. Beckett, Second Edition 
Oxform University Press. 



Chapter 









REPRODUCTION 
IN PLANTS 



4. REPRODUCTION IN PLANTS 




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REPRODUCTION IN PLANTS 

Do you know that all living organisms 
reproduce (both plants and animals)? wl 
Reproduction is a special biological 
process, by which new individuals of the 
same species are produced. It is one 
of the biological processes like nutrition, 
respiration and excretion etc. 

What will happen if there is no 
reproduction? 



Adult frog 



tadpole frog 





pulmonary 
breathing 
^ I front legs 

_yX tadpole break 




Fig. 4.1 Life cycle of Frog 



Some of the methods of reproduction in organisms are: 






1 Reproduction in anim^lBBJ^^^^B 


Peproduction in plcldH^| 


1 


Fission- Protozoan 


Fission - Bacteria 


Budding - Coelenterates 


Budding - yeast 


Fragmentation - Flatworms 


Fragmentation -Algae 




Spores -Fungi 


Sexual reproduction - Mammals 


Pollination and Fertilization - 
plants 


- Flowering 





REPRODUCTION IN PLANTS 




Fig. 4.2 Pollination and fertilization 
Questions 

1. What is meant by reproduction? 

2. Mention a few methods of 
reproduction in plants and animals. 

■ > 

South African fossil records show that 
the first formed organism in the Earth 
is a Bacterium, i.e, Eobacterium which 
came into existence approximately 
four billion years ago. In the past two 
billion years, life got diversified into 
multitude of varieties of organisms 
that exist today or existed and became 
extinct in the past, whereas bacteria 
continues to live as bacteria without 
much change. 



4.1. MODES OF REPRODUCTION 

4.1.1. Modes of reproduction in 
single cell organism 

Let us examine how different organisms 
actually reproduce. The methods by which 
organisms reproduce depend upon the 
body shape and structure of organisms. 

Unicellular organisms, like amoeba 
and bacteria, split into two equal halves 
and produce new ones which is called 
binary fission. 



Some Bacteria, like Lactobacilli, 
Salmonella multiply rapidly, others 
like Mycobacterium tuberculosis, 
multiply slowly. 



ACTIVITY 4.1 



• Wet a slice of bread and keep it in a 
cool, moist and dark place. 

• Observe the surface of the slice 
with a magnifying glass. 

• Observe for a week and record. 



Beneficial activity to humans : 

Conversion of milk into curd by 
Lactobacilli 

Harmful activity to humans : 

Bacteria like Mycobacterium 
tuberculosis cause tuberculosis. 



Amoeba 





Reproduction in unicellular organisms : 

By Fission 

^ ^ Bacteria ^ 

^ DNA Replication 

^ + Septum Formation 

^ Cell Separation 

"o o 

F\g. 4.3 Reproduction in unicellular organisms 



Think, read and analyse, 

why there are so many methods of re- 
production? 

Evolution may be defined as a grad- 
ual development of more complex 
species from pre-existing forms. On 
this basis, the reproduction in simpler 
forms, like Amoeba and Bacteria, is 
very primitive by means of Binary Fis- 
sion, Fragmentation, etc.. If, the com- 
plexity of the body design of organisms 
increases, the method of reproduction 
also gets complicated involving two 
organisms (male and female). 



ACTIVITY 4.2 



Observe a permanent slide of 
bacteria under a microscope. 

Similarly, observe another 
permanent slide of bacteria showing 
Binary Fission. 

Now compare the observations of 
both the slides. 



4.1.2. Modes of reproduction in 
multicellular organisms: 



1. Vegetative propagation 2. Asexual reproduction 3. Sexual reproduction 



1 




Pollination 



Fertilization 



Fragmentation Budding spores 

Depending upon the body organization 
of multicellular organisms, there are 
various methods of reproduction. 

Vegetative propagation: is the ability 
of plants to reproduce by bringing forth 
new plants from existing vegetative 
structures without sexual rproduction. 

Fragmentation 

In multicellular organisms with simple 
body organization, simple reproductive 
methods have been noticed. 

In Spirogyra algae, the plant body 
breaks up into smaller fragments. Each 
fragment grows into a new individual. 



Nucleus 
Septum 




Spiral 
Chloroplast 



Fig. 4.4 Fragmentation in spirogyra 



REPRODUCTION IN PLANTS 



ACTIVITY 4.3 



Collect water from a lake or pond 
that appears dark green and 
contains filamentous structures. 

Put one or two filaments on a slide. 

Put a drop of glycerin on these 
filaments and cover it with a cover 
slip. 

Observe the slide under a 
microscope. 



Budding 

In Hydra, a bud develops as an 
outgrowth due to repeated cell division at 
one specific site. These buds develop into 



tiny individuals and, when fully mature. 



Shoot 



get detached from the parent body to 
become new independent individuals. 

Similarly, buds produced in the notches 
along the leaf margin of Bryophyllum fall 
on the soil and develop into new plants (in 
Tamil katti pottal kutti pedum). 

4.1.3. Asexual reproduction 

In lower group of plants, reproduction 
takes place by means of spores. The spores 
are covered by thick walls that protect them 
until they come into contact with another 
moist surface and can begin to grow. 






Bud 



■Notch 



Aplanospores 



ri 



Zoospores 

f 




Fig. 4.5 Bryophyllum 



Akinetes Conldia 

Fig. 4.6 Different kinds of spores 



Some of the spores in different algae and fungi are 



APLANOSPORES ZOOSPOREf 



In algae, the protoplast 
of the vegetative 
cells contract and 
produce ovoid bodies 
surrounded by a thin 
wall. These thin walled 
non-motile spores are 
called Aplanospores. 
N ew filaments 
are formed by the 
germination of these 
spores. 



A zoospore is a motile 
asexual spore that 
uses a flagellum for 
locomotion. These 
spores are created by 
some algae, bacteria 
and fungi to propagate 
themselves. 



INETES 



In algae, the vegetative 
cells secrete thick 
additional wall layers. 
During adverse 
conditions, food 
materials are filled 
up in cells. These 
structures are called 
akinetes. When the 
Zable, they develop 
into new filaments. 



iNIDIA 



C n i d i a are 
uninucleate, non- 
motile, asexual spores 
produced by the 
fungus like penicillium, 
etc. 



Questions 

1. Differentiate vegetative 
propagation and sexual 
reproduction. 

2. Mention some of the spores of 
asexual reproduction. 

4.1.4. Sexual reproduction in plants 

What is sexual reproduction? 

Sexual reproduction is the process in 
which two components ( male and female) 
are involved to produce offsprings of their 
own kind. 

A bull alone cannot produce new calves. It 
needs a cow. Female sheep alone 
cannot produce new ones. It needs a 
male sheep. 

Both the sexes, male and female, are 
needed to produce new offspring. 

As you have already studied in your 
earlier classes, the flower is a 
reproductive organ of a flowering plant. 
To understand this we need to look first 
at the structure of a flower. 

Parts of a typical flower 

A flower is a modified shoot with a 
limited growth. Flowers vary in size, 
shape, structure and colour. 



The main parts of a flower are, 

1. Calyx 

2. Corolla 

3. Androeciunn and 

4. Gynoecium. 



Filament 



. Stigma ^^y'^ 
Anther / / Ovary 




rolla 



Calyx 

Fig. 4.7 Parts of a flower 




L Anther^ 
2. Filament 

Fig 4.8 Androecium 



Androecium is the male part of a 
flower,and Gynoecium is the female 
part. 



REPRODUCTION IN PLANTS 



Androecium is a group of stamens. 
Each Stamen consists of a stalk called 
the filament and a small bag like structure 
called the anther at the tip. The pollen 
grains are contained in the anther within 
the pollen sacs. 

Gynoecium 

Gynoecium is the female part of the 
flower and consists of the carpels or ovary. 
Gynoceium has three parts 1) Stigma 2) 
Style and 3) Ovary. 

The ovary contains the ovules and 
each ovule carries within it an embryo 
sac, within which lies the egg cell or the 
female gamete. 




Fig. 4.9 Gynoecium 



ACTIVITY 4.4 



Take a shoe flower from a growing 
plant. 

Observe the floral parts Calyx, 
Corolla, Androecium and 
Gynoecium. 

Separate the stamens and carpels 
and observe the parts. 

Dust the pollen grains on a 
slide and observe under the 
microscope. 



4.2. POLLINATION 

How does sexual reproduction take 
place in flowering plants? 

The sexual reproduction in flowering 
plants involves 

1. Pollination 

2. Fertilization 

1. Pollination 

Transfer of pollen grains from the 
anther to the stigma is called pollination. 
Pollen grains are transferred mainly by 
wind, water and insects. They are called 
as pollinating agents. 

Pollination is the first and important 
event in the development of the fruit 
and seed. Pollination is followed by 
fertilization. 

Types of Pollination 

Pollination is of two types. They are 

1. Self pollination 

2. Cross pollination 




Cross 
pollination 



^Self 
pollination 



^ Self 
pollination 



Fig. 4.10 Pollination 



4.2.1. Self Pollination 

Self pollination is also known as 
autogamy. The transfer of pollen grains 
from the anther of a flower to the stigma 
of the same flower or another flower of the 
same plant is known as self pollination. 



Advantages of self pollination 

1. Self pollination is certain in 
bisexual flowers. 

2. Flowers need not depend on agents 
of pollination. 

3. There is no wastage of pollen grains. 

Disadvantages of self pollination 

1. The seeds are less in number. 

2. Endosperm is minute. Therefore, 
the seeds produce weak plants. 

3. New varieties of plants cannot 
be produced resulting in the 
degradation of the plant. 



4.2.2. Cross Pollination (Allogamy) 

The transfer of pollen grains of a 
flower to the stigma of another flower of 
a different plant of the same species is 
called cross pollination or allogamy. 

Advantages of cross pollination 

1. The seeds produced as a result of cross 
pollination develop, germinate properly 
and grow into better plants, i.e., cross 
pollination leads to the production of 
new varieties. 

2. More viable seeds are produced. 



4.2.3. Agents of cross pollination 

How is it possible for the transfer of 
pollen grains from one flower to another? 

In order to bring about cross pollination, 
it is necessary that the pollen should be 
carried from one flower to another of a 
different plant. This takes place through 
agency of animals, insects, wind and water. 

Pollination by birds (Ornithophily) 
Pollination by insects and animals 



ACTIVITY 4.5 



Observe the flowers in a garden 
near to you. Identify the insects, and 
birds,that act as pollinating agents. 
Maintain a record detailing the pol- 
linating agents and the plants they 
pollinate 



Zoophily 

Animals and insects - Birds, squirrels 
and insects are attracted to the bright 
petals of the flowers. These flowers are 
also large in size and have a sweet smell. 
Some of these flowers have nectar and 
a sweet scent. This is the most common 
of all methods of pollination. This kind of 
pollination is called Zoophily. (Pollination 
by animals and birds). 




Fig. 4.11 Zoophily 



REPRODUCTION IN PLANTS 



Anemophily (Pollination by wind) 

The flowers pollinated by air are mostly 
small in size and without any attractive 
colour, smell and nectar. They produce a 
large number of pollen grains to make up 
for the wastage of pollen in times of transit. 




Fig. 4.12 Anemophily 

The pollen grains are dry and powdery, 
and hence are easily carried by the wind. 

Some pollen grains even have wings. 
Stigmas are large and protruding, even 
branched and feathery, e.g. Maize. 

Flowers pollinated by wind are called 
Anemophilous, e.g. Grass and pine. 



ACTIVITY 4.6 



Collect some of the zoophilous, 
anemophilous, hydrophilous 
flowers. 

Prepare a chart and make a note 
of their adaptations to suit the 
corresponding pollination. 



Pollination by Water (Hydrophily) 

This pollination takes place in water 
plants or plants that are adapted to water 
habitat, e.g. Vallisneria. This pollination 
is known as hydrophily. The flowers are 
small and inconspicuous. 




Fig. 4.13 Hydropliily 

4.3. FERTILIZATION 

Recall what you have studied about 
pollination. 

Pollination is the transfer of pollen grains 
from the anther to the stigma. Each pollen 
grain has protective walls called exine and 
intine. The outer wall exine is thick and it 
has small pores called germination pores. 
The inner wall is thin and elastic. 

Germination of pollen grain 

If pollen grain falls on a suitable 
stigma, it starts germinating. A mature 
pollen consists of two cells. The larger 
one is vegetative cell and the smaller 
one is generative cell. The vegetative cell 
starts growing and emerges through the 
germination pore. It develops through the 
style as a long tube known as pollen tube. 
The generative cell gets into the tube and 
divides into two male gametes (sperms). 



Pollen grain 



Pollen tube 




Sperm 
■Tube nucleus 



Fig. 4.14 Germination of pollen grain 



4.3.1. Process of fertilization 

The pollen tube enters into the embryo 
sac through micropyle. At this time, 
the pollen tube bursts open, gametes 
released from the pollen tube and enter 
into the embryosac. One of the gametes 
fuses with the egg, and the other fuses 
with the secondary nucleus. The fusion 
of a male gamete with egg is known as 
fertilization. The fertilized egg is known 
as zygote which develops into embryo. 



Pollen grain 
Style 



Ovule 




Pollen tube 



Embryo sac 



Fig. 4.15 Process of fertilization 

4.3.2. Double fertilization 

The other male gamete fuses with 
the secondary nucleus. The secondary 
nucleus is diploid in nature. 




Fig. 4.16 Double fertilization 

The fusion of this nucleus with the 
second male gamete is known as triple 
fusion. The triple fusion nucleus is called 
endosperm nucleus because it develops 
into endosperm. 



Endosperm is a nutritive tissue meant 
for the development of the embryo. The 
process of fusion of a male gamete with 
egg and the other gamete with secondary 
nucleus is known as double fertilization. 

4.3.3. Post fertilization changes : 

i. The ovule develops into seed, 
ii. The integuments of the ovule 

develop into seed coats. 
iii.The ovary enlarges and develops 

into fruit. 

4.4. FRUIT FORMATION 

You are all very familiar with fruits. They 
are inseparable with us in our day-to-day 
life. Fruits are rich in vitamin and give 
energy to us. Now let us discuss about the 
development of fruits and their types. 

As we discussed earlier, fruits are the 
product of fertilization. The ovary will 
become fruit after fertilization. It has two 
parts namely pericarp (fruit wall) and 
seeds. 

Some fruits develop without the act 
of fertilization. Such fruits are called 
Parthenocarpic fruits, e.g. seedless 
grapes, guava, mango etc. 

4.4.1. Classification of fruits 

The fruits are classified as follows: 

Simple fleshy fruits 

In simple fleshy fruits, the pericarp is 
succulent and juicy when fully ripe. The 
fleshy fruits are indehiscent in nature. The 
pericarp is distinguished into three parts, 
namely epicarp, mesocarp and endocarp. 
There are mainly two types of fleshy fruits 
- Baccate and Drupaceous. Baccate is 
further classified into berry, hesperidium, 
pome and pepo. 



REPRODUCTION IN PLANTS 



Simple dry fruits 

These fruits have a dry pericarp. 
They are classified based on mode 
of dehiscense as dry dehiscent, 
dryindehiscent and schizocarpic fruits. 

4.4-2. Dry dehiscent fruit 

These fruits split open at maturity to 
liberate the seeds. 

4.4.3. Dry indehiscent fruit 

These fruits do not split open at maturity 
and the seeds are liberated by the decay 
of pericarp 

4.4.4. Schizocarpic fruits 

At maturity, these fruits break into many 
one seeded parts called mericarps. The 
mericarps containing the seeds remain 
indehiscent. Thus the schizocarpic 
fruits show characters of dehiscent and 
indehiscent fruits. 

4.4.5. Aggregate Fruit 

It is developed from a single flower 
with multicarpellary, apocarpous, superior 
ovary. Each free carpel develops into a 
fruitlet. Hence, the aggregate fruit has a 
cluster of fruitlets attached to a common 
stalk (e.g) Polyalthia 

In Annona squamosa (custard apple), 
the margin of the carpels are united and 
appears like a single fruit. 



^^.-•i^ 



fV^lM 





Fig. 4.18 Custard apple 

4.4.6. Composite or Multiple fruit 

Multiple or composite fruit is formed 
by all the flowers of whole inflorescence 
and give a single fruit. There are two 
types of multiple fruits namely sorosis and 
syconus. 



ACTIVITY 4.7 



Collect a variety of fruits. Identify what 
type of fruit they belong to and make a 
note on them. 



Fig. 4.17 Polyaltliia 



Think, read and find out : 

Why are there so many varieties of 
fruits? 



4.4.7. Seed Formation 

Seed is a fertilized ovule. It possesses 
embryo, food materials and are protected 
by the seed coat. During favourable 
condition, the seed germinates and gives 
rise to a new seedling. 

Seeds have great variations in the size, 
shape, colour and surface. In orchids, 
there are many seeds which are tiny dust 
like particles. In coconut, there is a large 
sized seed. The seed grows into a full 
plant. 

On the basis ofthe number of cotyledons 
in the embryo (seed), the angiosperms 
have been divided into two groups. 



Simple fleshy fruits 



SI. No 



Type 



Diagram 



Description 



Baccate 
Berry 



Tomato 




It is one or many seeded fruit. 
Epicarp is thin and the mesocarp 
is fleshy. They form a pulp which 
is edible and the seeds are 
embedded in it. 



2. 



Hesperidium 



Orange 



It develops from multicarpellary, 
superior ovary with axile 
placentation. The epicarp is 
thick, leathery and contain oil 
glands. The whitish spongy 
layer lining the epicarp is called 
mesocarp. The endocarp forms 
distinct chambers. Juicy hairs 
produced from the endocarp is 
the edible part. 



Pome 



Apple 






/ 



The fruit develops from 
pentacarpellary syncarpous 

inferior ovary with many seeds. 
The thalamus becomes fleshy 
and develops into a fruit which is 
edible. The true fruit containing 
seeds remain inside 



It develops from a tricarpellary, 
syncarpous inferior ovary with 
parietal placentation.The pulp 
contains many seeds. 



4. 



Pepo 



Cucumber 




Drupaceous 
Drupe 



Mango 




It is a one seeded fleshy fruit and 
develops from monocarpellary, 
syncarpous ovary. The pericarp 
is differentiated into outer skinny 
epicarp,fleshy middle mesocarp 
and stony inner endocarp. Be- 
cause of the presence of stony 
endocarp, the fruit is also known 
as stone fruit. 



REPRODUCTION IN PLANTS 



Simple dry fruits 



Dry dehiscent fruits 



SI. No 



Type 



Diagram 



Description 



1. 



Legume 




^^iy- 



It develops from 

monocarpellary, unilocu- 
lar, superior ovary with 
marginal placentation. Peri- 
carp dehisces along both 
dorsal and ventral sutures 
(e.g.) pea, bean, etc. 



Follicle 



Calotropis 




It is like a legume fruit, but the 
pericarp dehisces along one 
suture only, (e.g.) Calotropis. 



Capsule 

(a) Septicidal 
capsule 



(b) Loculicidal 
capsule 



Cotton 




This is a many seeded fruit 
developing from superior 
or inferior, syncarpous 
multicarpellary ovary. 

Capsules dehisce by 
various methods. 



Lady's finger 




Dry indehiscent fruits 









SI. No 


Type 


Diagram 


Description 1 


1 


Achene 


Clematis, Mirabilis 


This is a single seeded fruit which 
develops from monocarpellary, 
unilocular ovary. Pericarp is hard 
and leathery, remains free from 
the seed coat 

1 




J 



Caryopsis 



Paddy 






-X tt"^ r: 7 






HKf\r 



It is a one seeded fruit which 
develops from superior mono- 
carpellary ovary. Pericarp is 
fused with the seed coat (e.g 
paddy, wheat, maize). 



Cypsela 



Tridax 




This fruit develops from in- 
ferior, bicarpellary syncar- 
pous ovary. The pericarp and 
the seed coat remains free 
(e.gTridax). 



Nut 



Cashew nut 




It is a dry indehiscent, one 
seeded fruit with hard and 
woody pericarp. Nut is devel- 
oped from superior, bi or multi- 
carpellary ovary (e.g. Cashew 
nut. Walnut etc). 







FRUIT 




1 

Simple fruit 

1 


1 

Aggressive fruit 


1 

Multiple 

1 


Fleshy fruit 

Baccate 

1 . Berry 

2. Hespsridium 

3. Pome 

4. Pepo 


Drupaceous 
Drupe 


Dry fruit 

Dry dehiscent 

1. Legume 

2. Follicle 

3. Capsule 

(i) Loculicldal 
(ii) Septicidal 


Sorosis Syconus 

Dry indehiscent Shizocarpic 

1 . Lomentum 

2. Cremocarp 

3. Regma 



REPRODUCTION IN PLANTS 



Schizocarpic Fruits 



SI. No 



Type 



Diagram 



Description 



1. 



Lomentum 



Acacia 




It resembles a legume and 
breaks transversely at con- 
strictions between the seeds 
(e.g Acacia). 



2. 



Cremocarp 



Coriandrum 




It is a two seeded fruit which 
develops from bicarpellary 
syncarpous, bilocular and in- 
ferior ovary. It dehisces longi- 
tudinally into two indehiscent 
mericarps (e.g) Coriandrum. 



Regma 



Castor 




It develops from tricarpellary 
syncarpous superior ovary 
and breaks up into three one 
seeded cocci (e.g Castor). 



Composite Fruits 



SI.No 


Type 


Diagram 


Description 


1. 


Sorosis 


Jack fruit 


In jack fruit, the rachis (inflo- 






^T'^, 


rescence axis) and other floral 






parts of the female inflores- 






■T* 


cence fuse together forming a 






K. z^ 


composite fruit. It consists of 
a fleshy central axis. The ed- 






^ -^ 


ible part represents the peri- 
anth which is bag like and one 
seeded. There are numerous, 
elongated, whitish flat struc- 
tures in between the edible 
flakes. They represent the ster- 
ile or unfertilized flowers. The 
pines on the tough rind repre- 
sent the stigma of the carpels. 



SI. No 


Type 


Diagram 


Description 


2. 


Syconus 


Fig 


It is derived from a special 






^^flHHHdiL^ 




type of inflorescence known 






TjH^Hk^ 




as hypanthodium which has a 






Ffli^^H 




fleshy receptacle. It has large 






^^^^^^H 




number of minute unisexual 






^^HHR 




flowers. On ripening, the 






\P^^^ 




receptacle becomes fleshy 








and juicy and forms the edible 








portion (e.g.) banyan, peepal , 








fig, etc. 



1. Dicotyledons: Seeds with two 
cotyledons (e.g) pea, bean, gram and 
castor. 

2. Monocotyledons: Embryo with one 
cotyledon (e.g) maize, rice, wheat and onion. 

1. Structure of a dicot seed (bean) 

The seed is bulky, oval and slightly 
indented on one side. On this side there 
is a short longitudinal, whitish ridge called 
the raphae. At one end of the raphae 
there is a minute opening known as germ 
pore or micropyle. 

If a water soaked seed is pressed 
gently a small drop of water along with air 
bubbles will be found coming out though 
the micropyle. 



Seed coat 



Cotyledons 

Radicle 

Endosperm 




Fig. 4.19 Dicot Seed (Bean) 



The embryo is enclosed by the seed 
coat. It consists of cotyledons attached to 
the primary axis which has rudimentary root 
portion called the radicle and a rudimentary 
stem portion known as plumule. 

The tip of the radicle projects outside ,and 
is nearer to the micropyle. The plumule is 
placed between the two cotyledons and 
consists of a short axis, and a small bud 
having two tiny little folded leaves. 

2. Structure of monocot seed (paddy) 

In paddy, the so called seed is actually 
a fruit. It is a simple indehiscent one 
seeded fruit known as caryopsis, (you have 
already studied about this in the lesson 
of fruits.).The seed coat is very thin. The 
fruit wall (pericarp) is thin and fused with 
the seed coat. The fruit is covered by 
generally yellowish bract and bracteoles 
which are commonly known as chaff. The 
embryo consists of single cotyledon called 
scutellum and a short axis. The lower 
part of the axis is the radicle, covered by 
a sheath called coleorrhiza (root sheath). 
The upper part is known as plumule which 
is covered by a sheath called coleoptile. In 
a day or two, after the seed is placed in a 
moist soil, the coleorrhiza pierces the base 
of the seed. The radicle comes out next 
after splitting the coleorhiza. 



REPRODUCTION IN PLANTS 



The radicle does not form the root 
system. Meanwhile, roots are formed 
from the lower most nodes of the stem. 
These roots are called adventitious roots. 
These adventitious roots form fibrous root 
system of matured plant. 



Seed coat 




Embryo 



Fig. 4.20 Monocot seed (Paddy) 



MORE TO KNOW 



Darwin used seeds of cress, 
cabbages, lettuces and onions. 
Darwin also studied longer 
periods in sea water, the effect 
of water temperature on 
germination and floating of seeds. 
His experiments overturned the 
idea that sea water kills seeds. Of 
the 87 species he used, Darwin 
found almost three-quarters of 
the seeds studied could tolerate 
solt water at least 28 days in salt 
water. 



ACTIVITY 4.8 



Label jars, filled with sea water and 
seeds. After 7 days put the seeds 
in a sieve, rinse under a tap, and 
plant out in labeled pots. 



ACTIVITY 4.9 



• Soak a few seeds of bengal gram 
(Channa) and keep them over night 
in a wet cloth. 

• Take care that the bengal gram is 
not swollen absorbing exess of 
water. ( The bengal gram should not 
be decayed with excess water. 

• Drain the excess water and cover 
the seeds with the wet cloth and 
leave them for a day. Make sure 
that the seeds do not become dry. 

• Cut and open the seed carefully and 
observe the different parts. 

• Compare your observations with the 
diagram and see if you can identity 
all the parts. 



4.5. Dispersal of seeds : 

The seeds fall off far away from the 
mother plant. Why? 

The reproductive capacity of plants is 
so tremendous that a very large number of 
seeds is produced by a single plant. If all 
these seeds fall directly below the parent 
plant, the seedlings would have to compete 
for space, water, oxygen, minerals and 
sunlight, leading to competition. When 
the seedlings are grouped together at one 
place, they could easily be destroyed by 
grazing animals. Such a situation would 
be detrimental to the species. 

The fruits and seeds of plants have 
evolved various devices by which they 
can be distributed far and wide through 
various agencies. 



This not only eliminates the unhealthy 
competitive struggle that would arise 
from over crowding, but also ensures the 
successful spreading and establishment 
of a species on the earth. Most fruits 
and seeds have evolved adaptations for 
dispersal. 

Agents for the dispersal of fruits and 
seeds: 

Based on the agents involved in 
dispersal, there are various types of 
dispersal mechanisms of fruits and seeds 
in plants. 

Autochory: Autochory is an active 
mechanism of self dispersal of fruits and 
seeds. Fruits like Balsam burst with a 
sudden jerk and disperse the seeds by an 
explosive mechanism. 

Anemochory is the wind dispersal of 
fruits and seeds. Alternatively, the wind 
may blow them away, for which they 
have to be light, so that their buoyancy 
may enable them to float on air over long 
distances. Some of them are provided 
with hairs and membranous wing-like 
structures which enable them to be carried 
away easily (e.g. Seeds dispersed by the 
wind are Calotropis (Erukkum), Moringa 
(drum sticks) etc.. 

Fruits of Tridax carry a persistent calyx 
modified into a pappus (a ring of fine, 
feathery hairs) which act like a parachute 
and aids in the dispersal by wind. 

Hydrochory: Hydrochory is a mecha- 
nism in which dispersal of fruits and seeds 
is by water. Fruits which are dispersed by 
water have outer coats that are modified 
to enable them to float. The mesocarp of 
coconut is fibrous, which is easily carried 
away by water currents. 



The spongy thalamus with air chamber 
of Lotus floats in water streams and after 
some time the fruits get separated, and 
the seeds germinate. 

Zoochory: Zoochory is a mechanism 
in which dispersal of fruits and seeds is 
by animals. Some fruits are provided with 
hooks, spines, bristles, stiff hairs, etc., 
on their outer coat. With the aid of these 
out growths, these fruits stick to the furry 
coats of skins of some animals and get 
carried away from one place to another. 

The fruits of Xanthium have sharp- 
pointed stiff hooks and the Achyranthus 
the perianth and bracts are pointed. Many 
fleshy fruits are eaten by animals and 
human beings and the seeds are thrown 
away. 




Fig. 4.21 Autochory (Balsam) 




Fig. 4.22 Anemociiory (Tridax) 



REPRODUCTION IN PLANTS 




Fig. 4.23 Hydrochory(Lotus) 




Fig. 4.24 Zoociiory(Xanthiium) 




In fruits like tomato and guava, the 
seeds are eaten along with the edible 
portion and later passed out by excreta. 
These types of seeds are protected from 
the digestive juices by their seed coat. 

Man is responsible for the dispersal 
of many fruits and seeds. In the pursuit 
of more economy, useful plants like 
Cinchona, Rubber and Eucalyptus have 
been successfully introduced by man and 
they have acclamalised well to the new 
surroundings far away from their original 
mother land. 



ACTIVITY 4.10 



Collect a few fruit or seeds which 
have wings. 

Observe the fruit of Tridax and 
draw. Look at the pappus calyx. 

Why is the mesocarp of coconut 
fibrous? 



Fig. 4.25 Zoociiory(Achyranthus) 



Collect some of the plants around 
you. What are their local names? 

Can you find out their botanical 
names? 



EVALUATION 



PART A 

1. This is the one of the methods of 
reproduction in unicellular organisms 
like amoeba and bacteria in which 
they split into two equal halves and 
produce new ones is called. 
(fragmentation, binary fission, 
budding, spore formation) 



2. In sexual reproduction of flowering 
plants, the first event involved in this is. 
(fertilization, germination, 
regeneration, pollination) 

3. Which of the following statement is true. 
(Thin walled non mobile spores 

are called zoospores, 
A motile asexual spore produced 
by some algae bacteria and fungi 
are Akinetes, 



Uninucleate non-motile asexual 
spores are produced by the 
fungus are called conidia, 
Thick walled vegetative cells 
produced by the algae during 
adverse conditions are called 
aplanospores.) 

4. The fertilized ovary is a fruit. The fruit 
develops from a single flower with 
multi carpellary, apocarpous superior 
ovary is 

(Aggregate fruit, Composite fruit, 
Simple fruit. Multiple fruit) 

5. If a water soaked seed is pressed, 
a small drop of water comes out 
through. 

(stomata, lenticel, micropyle, 
radicle) 

6. The mango fruit is called as stone 
fruit, because it has. 

(skinny epicarp, stony mesocarp, 

fleshy endocarp, hard endocarp) 

7. Pick out the wrong statement. 
(In a dicot seed there is a short 
longitudinal whitish ridge is called 
the raphae. 

There is a minute opening in dicot 

seed is known as micropyle. 

The rudimentary stem portion 

known as radicle. 

The rudimentary root portion is 

called radicle) 

8. Consider the following statement 
regarding the dispersal of fruit by wind 
and select the correct answer. 
(Fruits and seeds dispersed with 
a sudden jerk by an explosive 
mechanism. 



Fruits of tridax are carry a persistent 

calyx modified into pappus. 

The fruits of xanthium have sharp 

pointed stiff hooks. 

The mesocarp of coconut is fibres) 

9. The product of triple fusion which 
acts as nutritive tissue for the 
development of embryo is 
(zygote, placenta, scutellum, 
endosperm) 

10. The disadvantage of self pollination 
is 

(There is no wasteage of pollen 

grains. 

The seeds are less in number 

Self pollination is sure in bisexual 

flowers 

Flowers need not depend on agents 

of pollination 

PARTE 

11. a. Identify the given fig. A and B. 

b. Which part of the A is modified in 
to B. 



stigma 
^Style 

>^Ovary 



A B 

12. The methods of reproduction and 
the organisms are given below. 
Match the type of reproduction to 
the suitable organisms. 





Fission 


Spirogyra 


Yeast 


Budding 


Protozoans 


Flatworms 


Fragmentation 


Bryophyllum 


Bacteria 



REPRODUCTION IN PLANTS 



13. In balsam plant the seeds fall off far 
away from the mother plant. 

a) Is this statement correct or 
incorrect? 

b) Give reason. 

14. Composite fruits is formed by 
all the flowers of , 

fruit is developed from a 

single flower with multicarpellary 
apocarpous superior ovary. 

15. Redraw the diagram and label the 
following parts. 

a) Exine b) Tube nucleus. 




PARTC 

16. a) Name the process by which the 
fruit is developed. 



b)Give the development process in 

brief. 
c)Draw a neat diagram of that 

process and label. 

17. a) Write the two events involved 

in the sexual reproduction of 
flowering plant. 

b) Discuss the first event and 
write the types 

c) Give advantages and dis- 
advantages of that event. 

18. a) Fruit is the product of fertilization. Is 

there any fruit is formed with out the 
act of fertilization? 

b) Represent the classification of 
fruits in a diagrammatic sketch 

19. Compare aggregate fruit with multiple 
fruit with suitable examples. 

20. Describe the structure of dicot seed. 



FURTHER REFERENCE 
Books: 

1. Plant Reproduction - S.R.Mishra - Discovery Publishing House Pvt. Ltd. 



NAME OF THE PLANTS IN ENGLISH AND TAMIL 


S.No 


Botanical Name 


Connnnon Name in Engiisin 


Tamil Name 


How it is called locally 


1 


Abelmoscus esculentus 


Lady's finger 


Q6U6aOT6Q)l_ 




2 


Acacia coccina 


Soap acacia 


^m&s>&w[u 




3 


Acliyrantlies aspera 




r5rrLL|(rF)Q51 




4 


Anacardium occidentale 


Casliew nut 


(Lprfe^rfl 




5 


Anona squamosa 


Custard apple 


(^^rruuLpii) 




6 


Artocarpus integrifolia 


Jack fruit 


U60rr 




7 


Bryopliyllum 




SLi^u (EurrLLrrsi) (gili^u (Eurrgii) 




8 


Calotropis gigantea 


Madar plant 


5T(TF)(gB@ 




9 


Citrus sinensis 


Sweet orange 


(jrr^gij (96(5)1^ 




10 


Cocus nucifera 


Coconut 


Q^6(3T60)60T 




11 


Coriandrum sativum 


Coriandar 


Q(gBrr^gijLD6v36\51/^6Qfl Lurr 




12 


Gossypium arboreum 


Cotton 


U(TF)^^ 




13 


Cucumis sativus 


Cucumber 


Q6U etrsTTrflababrrLLj/ 
(B^rreo^cFaBabrrLLJ 




14 


Cucurbita maxima 


Pumpkin 


y,(?60Qfl(gB(gBrrLLj/ 
ujrEdaSlabdbrrLu/ 
^j(?rr 60)6001(96(96 rruj 




15 


Ficus glomerata 


Fig 


^^0 




16 


Impatiens 
balsamia 


Balsam 


u rr6i)Q(?600T®/u rr6b(? Li) 




17 


Lablab 
purpurreus 


Bean 


^6U60)J 




18 


Lycopersicon 
esculentum 


Tomato 


^(96(96 rr6iffl 




19 


IVIangifera Indica 


Mango 


mrr 




20 


IVIimosa pudica 


Touch me not plant 


"Q^rrLi_rr6v)6um^/ 
Q^mlLrr 60(5^(5 rEd (9^1/ 
Q^rrLi_rr6v3(^ ^)jr5J(9Sl " 




21 


IVIirabilis jalapa 


Four clock plant 


"^[B^iD[E»^rr60)j/ 

^[B^lD6V36\5l60)(9b" 




22 


Nelumbo nucifera 


Indian lotus 


^rrLD60)j 




23 


Oryza sativa 


Paddy/ rice 


Qr56v3 




24 


Pisum sativum 


Pea 


ULi_rr60ofl 




25 


Polyaltliia longifolia 


Mast tree 


Qr5Li^6\51r5J(9bLi) 




26 


Pyrus malus 


Apple 


^Ljdl6tT 




27 


Ricinus communis 


Castor 


^lD600T(9b(g,/ 
(Lp^glJ(9BQ(9Bml60)l_ 




28 


Tridax 




Q6UL_®(gB(9bmuiJ y,600T®(J Q(?i^ 





Chapter 







L 




r 







A REPRESENTATIVE 
STUDY OF MAMMALS 



5. AFe^RBBSnATl VESTUDf OF 

MAMMALS 



Mammals are the diverged group of 
animals, occupying different biomes of the 
environment , successfully fitting in their 
habitats. Mammals are found almost in 
all habitats like oceans , freshwater, hilly 
regions , forests, deserts, polar regions 
and swamps. 

5.1. MORPHOLOGY 

Mammalian morphology is so divergent, 
as they occupy different habitats . The sea 
living dolphins, whales etc., look like fish, 
by form and structure. A nocturnal bat 
gliding in the sky, looks like a bird. All the 
large land animals are mammals. The size 
of mammals sets them apart from all other 
kinds of land animals. 

Mammals are distinguished from 
other vertebrates by two fundamental 
characteristics that all mammals possess 
and no other living vertebrate possess. They 
are 

1. Epidermal Hairs 

2. Milk producing glands. 

Epidermal Hairs 

All mammals have hairs, even 
apparently naked whales and dolphins 
grow sensitive bristles on their snouts. 
Mammalian hair is a new form of skin 
structure a derivative from the skin; the 
hair is an insulator against heat loss. 
The colouration and pattern of mammal's 
skin usually matches its background. 
Hairs also are sensory structure, as the 



whiskers of cats and dogs are sensitive to 
touch. Hair is also defensive for porcupine 
and hedgehogs with long, sharp, stiff 
hairs called quills to protect them from 
predators. 



ACTIVITY 5.1 



Observe the hair of dog, cat, catties, 
man, horse and donkey. Look for the 
structural details like shape, texture 
and curly or straight condition and 
record your findings. 



m 



Milk producing glands 

All female mammals possess mammary 
glands that secrete milk. New born 
mammals, born without teeth suckled by 
the mother. Milk producing glands are 
modified sweat glands. 

5.2. HABITAT 

The place of living of an organism is its 
habitat. Mammals exhibit a great degree of 
functional adaptation to fit in the habitats in 
which they live. We find mammals living in 
high mountains, plains and forests, tundra, 
grassland, deserts, fresh water and marine 
habitats. Some important mammals in their 
different habitats are listed below; 



High mountains 



Plains and forests 



mountain goats, big 
horned sheep, grizzly 
bears, etc., 

porcupine, giant 
squirrel, deers. 



A REPRESENTATIVE STUDY OF MAMMALS 



elephants, 
tiger, leopard, 
rhinoceros. 
Hippopotamus, 
etc.. 

Tundra - reindeer, muskdeer 
ox, rodents, etc.. 



Desert 


- black buck, Indian wild 




ass etc., 


Fresh water 


- beavers, platypus. 




otters, etc.. 


Marine 


- whales, dolphins. 




dugong, porpoise, seal. 




walrus, etc.. 




Fig. 5.1 Diverged group of mammals with their young ones 



5.3. MAMMALIAN ADAPTATIONS 

Mammalian group is the most 
successful animals adapted to different 
conditions of life. 

i) In the marine whales, dolphins, etc,, 
the limbs are modified into flippers 
which are used as oars to swim in 
water. They also posseses huge 
subcutaneous fat deposits to 
conserve heat. The jaws of the whales 
are modified into baleen plates to 
sieve the water and trap the minute 
planktonic organisms as their food 
called krill. 

ii) The skin of camels is doubly thick 
and contains water storing osmotic 
cells to conserve water, as they live 
in deserts. They have thick bunchy 
eyebrows covering the eyes to 
protect the eyes from sandy wind. 
Their nasal hole can be closed during 
desert storms to prevent the entry of 
sand particles. 

iii) Most mammals are herbivores, 
eating mostly or only plants. To digest 
the cellulose rich food, they have 
developed a mutual partnership with 
bacteria that have cellulose splitting 
enzymes. 

iv) Mammals such as cows, buffaloes, 
antelopes, goats, deers, etc,, have 
huge four chambered stomachs that 
function as storage and fermentation 
vats. The stomach of catties also 
helps them to ruminate or cud the 
food. 



v) Mammals have heterodont dentition 
with different types of teeth that are 
highly specialized to match particular 
eating habits. For example, the 
carnivorous animals have tearing 
teeth - the canine. In elephant the 
incisors are modified into tusks as a 
specialized weapon. 

vi) Bats are the only mammals capable 
of powered flight. The forelimbs 
of bats are modified into wing like 
structure. The bat's wing is a leathery 
membrane of skin and the muscle 
is stretched over the bones of the 
four fingers. Bats prefer to hang 
upside down from their legs while 
resting. The nocturnal bats can fly 
without crashing into things and still 
capture insects by echo location. As 
a bat flies, it emits very rapid series 
of extremely high pitched clicking 
sounds. The sound waves bounce 
off objects or flying insects and the 
bat hears the echo. 

vi) The marsupials, kangaroo have 
developed abdominal pouches to 
bear the tender young ones. 

vii) The polar bears have thick skin coats 
and woolly fur to bear the biting cold 
of the polar regions. 

viii) The supreme mammal - man is 
highly adapted as an intellectual 
social animal. The fingers and toes 
are adapted for handling extremely 
fine movements in holding of fine 
objects, in writing and using very 
delicate instruments. 



A REPRESENTATIVE STUDY OF MAMMALS 




Fig. 5.2 Bat 

5.4. BASIC PHYSIOLOGICAL 
FUNCTIONS 

Mammals perform the physiological 
functions more efficiently compared to 
other vertebrates. 

Mammals are warm blooded or 
homeotherms, maintaining a constant 
body temperature, irrespective of the 
temperature in the surroundings. The body 
temperature in man is maintained at 98.4° 
F to 98.6° F. The temperature regulation is 
done as a team work, by the sweat glands 
of skin, kidneys, lungs and blood. 

In summer, we sweat more as a cooling 
up mechanism, to conduct the heat out 
in the sweating process. This is possible 
with increased blood supply to the sweat 
glands. The kidneys expel less urine since 
much of water is lost in the sweat. 

In winter, we produce little sweat as 
a warming up mechanism to conserve 
heat. The sweat glands are supplied with 
less amount of blood, so that the amount 



of heat lost is lowered. Now the kidneys 
excrete out more urine. 

Mammalian respiration is more efficient 
in comparison to other vertebrates. Red 
blood cells of mammals are fully packed 
with the respiratory red blood pigment 
haemoglobin, to carry the maximum 
amount of oxygen. The mammalian 
RBCs are without nucleus, as the space 
occupied by the nucleus is taken up by the 
haemoglobin molecules. 



ACTIVITY 5.2 



Note the body temperature of some 
of your classmates at 10 a.m, 1 p.m 
and 4 p.m. Record the same. Do you 
find any change in the temperature at 
different timings? 



5.5. CIRCULATORY SYSTEM 
OF MAN 

In order to transport substances from 
one part of the body to the other, the 
circulatory system has evolved. In man, 
the circulatory system is composed of 

i) the heart 

ii) the blood vessels namely arteries, 
veins and capillaries 

iii) the blood and 

iv) the lymph. 

William Harvey in 1628 discovered the 
circulation of blood in man, until then it 
was thought that the body is a blood filled 
entity, and the blood is stagnant in it. 




William Harvey 1578-1657 was an 
English physician. He was the first to 
give the details of blood circulation, 
the properties of blood and the 
pumping of blood by the heart. 



The heart 

The human heart is a hallow fibre 
muscular organ. It is conical in shape, 
the heart is covered by a protective 
double walled sac called pericardium 
filled with pericardial fluid. The heart 
is made up of special type of muscles, 
called cardiac muscles. The partitions 
within the heart divide the heart into four 
chambers as auricles and ventricles. 
The right half of the heart receives and 
pumps off deoxygenated blood and the 
left half of the heart receives and pumps 
out oxygenated blood. 

Auricles 

These are thin walled upper 
chambers. The auricles are divided into 
a right auricle and a left auricle, by a 
partition called inter auricular septum. 
Auricles are the receiving chambers 
of blood. Into the right auricle open 
the superior venacava and inferior 
venacava emptying the deoxygenated 
blood brought from different parts of 



the body. Into the left auricle open the 
four pulmonary veins emptying the 
oxygenated blood brought from the 
two lungs. 

Ventricles 

These are thick walled lower 
chambers of the heart. A partition 
called inter ventricular septum divides 
the ventricle into right and left ventricle. 
The ventricles pump the blood out 
from the heart. From the right ventricle 
the deoxygenated blood is pumped 
into pulmonary artery to supply the 
two lungs. From the left ventricle 
oxygenated blood is pumped into the 
aorta to supply the oxygenated blood to 
the different parts of the body through 
its branches. 

Apertures of the heart 

Between the right auricle and right 
ventricle is found the right auriculo 
ventricular aperture and between the 
left auricle and left ventricle is found the 
left auriculo ventricular aperture. 



Superior 
vena cava 



Right 
atrium 



Tricuspid 
valve 



Right 
ventricle 

Inferior 
vena cava 




Aorta 



— Pulmonary 
artery 

Left Pulmonary 
I /veins 

Left 
atrium 
Semi - 
lunar valve 
Mitral valve 

Left 
ventricle 



Cardiac 
muscle 



Fig. 5.3 Human heart 



A REPRESENTATIVE STUDY OF MAMMALS 



Valves of the heart 

A tricuspid valve with three flaps is 
found in the right auriculo ventricular 
aperture to regulate the flow of blood, 
from right auricle to right ventricle and 
not backwards. 

A bicuspid valve or mitral valve with 
two flaps in the left auriculo ventricular 
aperture regulates the flow of blood, 
from left auricle to left ventricle and not 
backwards. 

At the base of the pulmonary artery 
is present the semi-lunar valve, which 
regulate the blood to flow from the right 
ventricle to the pulmonary artery. 

At the base of the aorta is present the 
aortic valve, to regulate the flow of blood 
from left ventricle into aorta. 

Working of heart 

Human heart works by contraction 
and relaxation of the cardiac muscles. 
The contraction phase is called systole 
and relaxation phase is called diastole. 

When the auricles are filled with blood 
they are in relaxation phase (auricular 
diastole). By now ventricles will push the 
blood into aorta and pulmonary artery by 
their contraction (ventricular systole). 

When the auricles contract (auricular 
systole) the blood is pushed into the 
ventricules through the bicuspid and 
tricuspid valves, leading to ventricular 
relaxation (ventricular diastole). 

Heartbeat 

The closure of the valves of the heart 
produce two different cardiac sounds 



as "lubb" and "dubb'\ The human 
heart beats 72 times in a minute at rest. 
Heartbeat is an inherent capacity of 
the heart, begun and conducted by the 
specialized muscle bundle in the heart. 

Blood vessels 

There are three distinct types of 
blood vessels, namely, arteries, veins 
and capillaries. 

Arteries 

Arteries carry the blood from the 
heart to different parts of the body. 
They are the branches of aorta, 
supplying oxygenated blood to the 
different regions of the body (except 
pulmonary artery which carries 
deoxygenated blood). The aorta 
branches into arteries. Arteries branch 
into arterioles. Arterioles branch into 
fine tubes called meta arterioles. The 
meta arterioles end up in the tiny blood 
vessels called capillaries. 



Capillaries 




-Arteriole 



Fig. 5.4 Arteries, capillaries and veins 



Capillaries 

These tiny blood vessels form a 
network, called capillary network around 
the tissues to enable the passage of 
substances from the blood into the tissues. 

Veins 

The veins drain the blood from 
different parts of the body to the heart. 
The capillaries reunite to form venules, 
which drain the deoxygenated blood from 
the tissues. The small venules united 
with the big veins open into superior 
venacava and inferior venacava. 
Except the pulmonary veins all other 
veins carry deoxygenated blood. 

The blood 

Blood is the river of life - providing the 
internal environment to the body. Blood is 
the connective tissue, consisting of the fluid 
part, the plasma and the solid components, 
the blood cells. 

Plasma 

The liquid component of blood, the plasma 
is composed of water, organic substances, 
inorganics substances, etc,. The important 
organic substances of plasma are the 
plasmaproteins namely globulin (for 
immunity), fibrinogen (for blood clotting) 
and albumin (for water balance). 

Blood cells 

There are three types of blood cells 
namely Red Blood Cells, White Blood 
Cells and Blood Platelets freely floating in 
the plasma. 

Red Blood Cells -Erythrocytes 

RBCs are circular, biconcave and 
disc shaped. While the young RBCs 



have nuclei, the matured ones are 
without nuclei. The red blood pigment 
haemoglobin is fully packed in the RBCs. 
They are concerned with carriage of 
respiratory gases. 

White Blood Cells - Leucocytes 

WBCs are amoeboid in shape with 
prominent nuclei. WBCs are concerned 
with phagocytosis of engulfing the germs 
and producing antibodies to resist the 
germs entering the body. 

Blood Platelets - Thrombocytes 

Platelets are irregular broken up pieces 
of certain giant cells. They are concerned 
with blood clotting to prevent the loss of 
blood. 



H 




/aX 


V 


Platelets 


Red blood 


^ 


cells 


5 


(? 


Neutrophil 


Monocyte 


• 


% 


Lymphocyte 


Eosinophil 


n' 


Basophil 



Fig. 5.5 Blood Cells 



A REPRESENTATIVE STUDY OF MAMMALS 



5.6. EXCRETORY SYSTEM IN MAN 



HgKgigMJ^tJU^ 




^^iwmm^^ 


Kidneys 


Nitrogenous waste products - 
urea, uric acid, creatinine, etc,. 


Urine 


Lungs 


Carbondioxide and 
water vapour 


Expired air 


Skin 


Excess water and salt 


Sweat 



Excretion is the removal of metabolic 
waste products called excreta. The 
important excreta and the excretory organs 
which remove them are shown in the 
above table. 

The principal excretory organs of our 
body are the kidneys, which maintain the 
chemical composition of the blood and so 
are called as master chemist of our body. 

External structure of kidney 

A pair of kidneys are present in the upper 
abdominal region, one on either side of the 



vertebral column attached to the dorsal 
body wall. A thin transparent membrane 
called capsule covers the kidney. The 
kidneys are bean shaped with outer 
convex surface and inner concavity. The 
depression in the concavity is called renal 
hilus, from which arises the muscular tube 
called ureter. The two ureters open into 
the distensible muscular sacs called the 
urinary bladder which is the store house of 
urine. From the urinary bladder arises the 
urethra which delivers the urine out of the body. 



Inferior 
venacava ^^ 

Pe\V\s^/^!!l^ 

Medulla Ml 
Cortex 



Adrenal 
gland 




Renal 
artery 

Renal vein 
Kidney 



Ureter 



Urinary 
bladder 



Urethra 



Renal 
column 



Cortex . 

Renal 
capsule 



Medullary 
pyramid 




Calyx 

Renal 
artery 

Renal vein 

Pelvis 
— Ureter 



Fig. 5. 6 Excretory system of man 



Fig. 5. 7 LS of Kidney 



Internal structure of kidney 



Malpighian capsule 



The outer portion of the kidney is dark in 
colour and is called renal cortex and inner 
pale region of the kidney is called renal 
medulla. Renal medulla contains conical 
masses called renal pyramids. On the renal 
pyramids are found the openings called 
renal papillae, which open into the inner 
space of the kidney called renal pelvis. 
From the renal pelvis arises the ureter. 

The kidneys are composed of millions 
of units called nephrons. 

Structure of a nephron 

Nephrons are the structural and 
functional units of the kidney each kidney 
is composed of millions of nephrons. A 
nephron has two structural components 
namely, Malpighian capsule and the 
uriniferous tubules. 



Glomerulus 



Bowman's 
capsule 




Distal ^ , 

convoluted tubule i f 



Proximal 

Convoluted 

tubule 



Loop of — 
henle 



Collecting duct- 



^ 



V 




F\g. 5.8 Nephron 



This consists of a network of blood 
capillaries called glomerulus and a 
double walled cup called Bowman's cup. 
The glomerulus is a network of blood 
capillaries, formed by the branches of the 
wider afferent renal arteriole. From the 
glomerulus arises the narrow efferent renal 
arteriole, which branches over the rest of 
the nephron as network of capillaries. The 
Bowman's capsule accommodates the 
glomerulus. 

Uriniferous tubules 

From the Bowman's capsule arises 
the Uriniferous tubules. It is divided into 
three portions as the initial coiled proximal 
convoluted tubule, the middle U-shaped 
Henle's loop and the later coiled distal 
convoluted tubule. The distal convoluted 
tubule straightens as the collecting ducts. 
The collecting ducts open on the renal 
pyramids as renal papillae. The nephrons 
filter the blood and form the urine. 

5-7-RELATIONSHIP OF 

STRUCTURE AND FUNCTION 

Based on the functional need a particular 
organ or part gets a suitable modification 
in its structure. Thus a structure is so 
adapted to perform a specific function. So 
structure and function go hand in hand. 
The fore limbs of different mammals are 
suitably modified to do different functions 
according to their environment. For 
example, all the vertebrate animals in 
general, and all mammals in particular, 
have their fore limbs sharing a common 
basic pattern of construction. The fore 
limbs of mammals consist of five parts 
namely upper arm, fore arm, wrist, palm 



A REPRESENTATIVE STUDY OF MAMMALS 



and phalanges, but they are differently 
used in different animals like 

i) Man uses his fore limb to hold an 
object, write, operate very fine 
musical instruments and delicate 
digital devices. The thumb is deviant 
from other four fingers, to enable 
man to do the above jobs. 

ii) A horse uses it's fore limb to gallop. 

iii) A rat or bandicoot uses it's fore limb 
to make holes in the ground to live. 

iv) A giraffe uses its pretty long and 
stout fore limbs to reach up the 
vegetations, at the height of the 
plants. 

v) A monkey leaps from one branch 
of the tree to another using it's fore 
limb to swing and leap. 

vi) A whale uses its fore-limbs as oars 
to swim. 




Human Frog 



Porpoise Horse 



Fig. 5.9 Basic pattern of 

forelimbs of vertebrates 



5-8- ANIMAL BEHAVIOR 

Behaviour can be defined as an 
organism's adaptive response to stimuli in its 



environment. The stimuli may be as simple 
as the odour of the food. Nervous system 
perceives and passes the information 
concerning the environmental stimuli and 
trigger adaptive motor response which we 
see as the patterns of behaviour. 

5.8.1. Social behavior 

Behaviour is both an instinctive process 
(influenced by genes) and learned 
experience (gained by experience). 

Social attachments between animals 
is called imprinting. The binding or 
attachment between the parents and the 
offspring is called filial imprinting. At times, 
we find an individual of a species is raised 
by a parent of another species (e.g the 
chick of cuckoo bird is fed by crow in its 
nest). This behavioural pattern is called 
cross fostering. 

Many insects, fish, birds and mammals 
live in social groups in which information 
is communicated between group 




Fig. 5.10 l-loney Bee 

members. For example some individuals 
in mammalian societies serve as guards. 

In an elephant herd, it is always the 
oldest she elephant that leads the herd. 



while the strong males will form the periphery 
of the herd and the young calves and other 
she elephants will be in the centre. 

Sexual behavior 

The coming closer of the opposite 
sexes is both by instinctive process and 
sexual attraction exhibited by one or 
both the partners. The secondary sexual 
characters developed during the breeding 
season bring the two sexes together for 
sexual reproduction. For example , the 
bright and colourful plumage of male 
peacock is to draw the attention of the 
female. 

Sexual imprinting 

Is a process in which an individual 
learns to direct its sexual behaviour at a 
member of its own species. During the 
courtship, animals produce signals to 
communicate with potential mates and 
with other members of their own sex. A 
character exhibited by one sex to attract 
the other sex is called courtship signalling. 
Many courtship signals are species, 
specific to help animals avoid making 
errors in mating. 

Parental care 

Any investment or effort by the parent 
to take care of the young ones in order 
to increase the chance of survival 
of the offspring and hence increase 
the reproductive success is called 
parental care. The parents care for the 
young ones and provide high nutrition, 
protect the young ones from predators 
and enable the young ones to lead a 
successful life. 



Providing the young one with the milk 
from its mammary gland and aggression 
exhibited against the predator are the best 
means of taking care of the young one. 
Even after the nutritional independency is 




Fig. 5.11 Parental care in elephiants 

obtained by the young one i.e it takes care 
of its nutrition by itself, the parental care 
is extended in some species beyond this 
level. 

5.9. A CASE STUDY BY A 
RESEARCHER 

The behavioural patterns in different 
situations are investigated in the research 
projects taken up by leading universities 
in Tamilnadu. 

The abstract of case study by 
Arun Venkatraman, Asian Elephant 
Conservation Centre, Centre for Ecological 
Science, Indian Institute of Science - 
Bangalore on Dholes is given below. 

Courtesy to the researcher - Mr.Arun 
Venkatraman) 

Asiatic wild dog (Chen Nai - in Tamil), 
commonly called Dholes - Cuon 



A REPRESENTATIVE STUDY OF MAMMALS 



alpines is an endangered species 
living in Mudumalai Wildlife Sanctuary 
at Nilgiris, Tamilnadu. 

The Dholes live in packs which consist 
of old females, males, females and pups. 
The pack members co-ordinate while 
pulling down and killing large prey such as 
adult Sambar Deer. There is a tendency to 
share the meat among the members of the 
pack. However there prevails a squabbling 
among them to get the choicest meat. 
The young pups are allowed to take 
the meat first. The old males follow 



ACTIVITY 5.3 



CASE STUDY 

• Conduct a case study on the 
behavioural aspects of your pet 
dogs in reference to their territorial 
dominance when strangers or other 
dogs try to enter into your locality. 

ACTIVITY 

• Follow an ant line and try to break 
its route by drawing a line with your 
finger without killing any ant. 

• Observe the behaviour of the ants 
as to whether they change the route 
or go in disarray. 

• Try to observe for a few minutes 
for any change they resort in 
their route. Make a report of their 
behaviour and submit. 



them. The other young ones and old 
females usually lag behind. 

The Dholes also exhibit a high 
degree of parental care by changing 




Fig. 5.12 Dholes 

the den frequently so that the pups are 
safe from predators such as leopards 
and hyenas. 

• functions efficiently. 

• Behaviour is the adaptive response 
of an organism to the stimuli in the 
environment. 

• Social behaviour is both instinctive and 
learned experience. 

• Sexual behaviour involves courtship 
signalling which is species specific. 

• The investment or effort by the parent 
on their offsprings to provide nutritive 
food and safeguard them from 
predators is called parental care. 



EVALUATION 



PART A 

1. Sensitive whiskers are found in 



Bat, Elephant, Deer, Cat. 
2. The tusks of elephants are modified 



3. Pick out an animal which has four 
chambered stomach . 

Elephant, Dolphin, Deer, Kangaroo. 

4. Normal body temperature of man is 



98.4 - 98.6°F, 96.6 - 96.8°F, 94.4 - 
98.6°F, 98.4 - 99.6°F. 

5. Mitral valve is found between 



Right auricle and right ventricle. Left 
auricle and left ventricle. 

Right ventricle and pulmonary artery. 
Left ventricle and aorta. 

PARTE 

6. One of the following groups contains 
a non mammalian animal. Pick up the 
group. 

a. dolphin, walrus, porcupine, rabbit, bat 

b. elephant, pig, horse, donkey, 
monkey 



c. antelope, deer, cow, buffalo, black buck 

d. dog, cat, crocodile, lion, tiger 

7. The epidermis of mammals contains 

a. hair, bristle, quills 

b. hair, nail, claw 

c. hair, bristle, horn 

d. hair, nail, scale 

8. Based on relationship, fill up: 
Whale: Baleen plates; Bat : 

9. Fill in the blanks. 

Plasma : Fibrinogen ; RBC : Carrier 
of oxygen; WBC: 

10. Master chemists of our body are 
kidneys. Justify. 

a. kidneys acquire all chemicals taken 
in the body 

b. maintain the chemical composition 
of blood 

c. kidneys send out all chemicals taken 
in the body 

d. kidneys store the various chemicals 
taken in the body 

11 . Based on modifications make the pairs: 
incisor: tusk of elephant; 
: quills of porcupine. 



FURTHER REFERENCE : 








Books: 












1. 


Biology 


- RAVEN, Johnson WCB Mc Graw - 


Hill 


2. 


Biology 
Oxform 


- A Modern Introduction, 
University Press. 


B.S. 


Beckett 


, Second Edition 





6.LIFEPR0CBSES 



How do you differentiate the living 
things and non-living things? 

If we see a dog running 

(or) 
a cow chewing cud 

(or) 

a man shouting loudly on the street, 

We know that these are living beings. 

What if the dog or the cow or the man 
were asleep? 

We would still think that they were alive, 
but how did we know that? We see them 
breathing and we know that they are alive. 

What about plants? 

How do we know that they are alive? 

We see their green leaves and some 
kind of movements like the folding and 
unfolding of leaves, stages of growth as 
common evidences for being alive. 

6.1. WHAT ARE LIFE PROCESSES? 

The maintenance of living organisms 
must go on even at the conditions, when 
they are not physically active. Even when we 



sit idle and during sleeping, this maintenance 
job through cells functioning has to go on. 
The life process includes the activities 
performed by the different organs to 
maintain the body. 

Some of the life processes in the living 
beings are described below: 

Nutrition 

The processes of obtaining energy 
through consumption of food. 

Respiration 

The process of acquiring oxygen through 
breathing and make it available to cells for 
the process of breaking down of organic 
substances into simpler compounds is 
called as respiration. 

Transportation 

Transportation is the process by which 
the food and oxygen is carried from one 
organ to other organs in the body. 

Excretion 

It is the process by which the metabolic 
waste by-products are removed from the 
different organs and released out from the body. 




How do we understand the living 
nature of organisms? 

2. What are the materials available from 
external sources for the organism's 
consumption? 

3. What processes are essential to 
maintain our body? 

6-2- NUTRITION IN PLANTS 

Do you know that we need energy for 
all activities? 

When do we get that energy? 

The source of energy is the food we eat. 

Types of Nutrition 

Autotrophic Nutrition 

Most of the green plants are self- 
dependent, because they synthesize their 
own food materials by photosynthesis. 
Such mode of nutrition is described as 
autotrophic nutrition. 

It is the process by which autotrophic 
plants consume substances from the 
external sources and convert them into 



stored form of energy. The materials 
are taken in the form of carbon dioxide 
and water which are converted into 
carbohydrates in the presence of light and 
chlorophyll. Carbohydrates are utilized as 
energy rich sources to the plant., for their 
entire activity. 

The process of photosynthesis is 
explained in the form of bio-chemical 
reaction shown below: 

Chlorophyll 



6CO2+I2H2O ► C6Hl206-^602-^6H20 

Sunlight (Glucose) 

The raw materials and other necessary 
items required for photosynthesis are 
Sunlight, Water, CO^ and Chlorophyll. 

Sunlight - energy from the sun 

Water - plant absorbs water from 

the soil through roots. 

CO2 - assimilated from the 

atmosphere through leaves 
containing small pores 
called stomata. 

Chlorophyll - the green pigments in the 
chloroplasts, an organelle 
of the cells of leaf. 



LIFE PROCESSES 



u 



Let us do an activity which demonstrates that chlorophyll is essential 
for photosynthesis 



ACTIVITY 6.1 



1. Take a potted plant with variegated leaves - for example, money plant or 
crotons. 

2. Keep the plant in a dark room for three days so that all the starch gets 
used up. 

3. Now keep the plant in sunlight for about six hours. 

4. Pluck a leaf from the plant. Mark the green areas in it and trace them on a 
sheet of paper. 

5. Dip the leaf in boiling water for a few minutes. 

6. After this, immerse it in a beaker containing alcohol. 

7. Carefully place the beaker in a water-bath till the alcohol begins to boil. 

8. What happens to the colour of the leaf? What is the colour of the solution? 

9. Now dip the leaf in a dilute solution of iodine for few minutes. 

10. Take out the leaf and rinse off the iodine solution. 

11. Observe the colour of the leaf and compare this with the tracing of the leaf 
done in the beginning. 

12. What can you conclude about the presence of starch in various spots of 
the leaf? 



Heterotrophic nutrition 

Fungal cells do not contain chloroplasts 
and they formed into saprophytes and 
parasites. Likewise all organisms, exceptthe 
green plants do not possess chloroplasts as 
they do not carry out photosynthesis. They 
depend upon plants or other organisms for 
their nutrition. 



The plants or animals in which the 
parasites live for nourishments are called 
hosts. Parasitic plants have some special 
roots, which penetrate the host plants and 
absorb food from the phloem, water and 
minerals from xylem. These roots are called 
haustoria. (e.g.: Cuscutta and Viscum). 

Saprophytes 



Parasites Some plants obtain nutrients from non- 

Some organisms live on other organisms "^'"9 ^^9^^'^ ^^"er. They are called 
for nourishments. They are called Parasites, saprophytes. Many fungi and bacteria are 



saprophytes. Certain angiosperms like 
Monotropa lack chlorophyll and have 
mycorrhizal roots.The plant absorbs 
nourishments from the humus through 
their mycorrhizal roots. 




Fig. 6.1 Variegated Leaf 
(a). Before starcli test (b). After starch test 





Fig. 6.2 Cuscutta - a parasitic plant 



Fig. 6.3 Viscum - a parasitic plant 

Questions 

1. What are the differences 

between autotrophic nutrition 
and heterotrophic nutrition? 

2. What are the sources of 
materials required by plants for 
photosynthesis? 

6.2. HUMAN DIGESTIVE SYSTEM 

Intracellular digestion 

White blood cells (leucocytes) in 
vertebrate animals are defensive in 
functioning and get rid of germs in the body 
of the animals. WBCs engulf the invading 
germs by producing pseudopodia around 
the germs and digest the germs inside 
them by phagocytosis. 

The unicellular animalcules like 
Amoeba also produce pseudopodia to 
engulf the diatoms and other minute 
organisms and digest them within the cell. 
Paramoecium, an another protozoan has 
a cytopharynx, a cytoplasmic depression 
to swallow the food (i.e microorganisms 



LIFE PROCESSES 



u 



in water) and digest the food within the 
cells. In the above mentioned examples 
the food is directly taken into the cells 
and is digested within the cell. This sort of 
digestion is called intracellular digestion. 
Intracellular digestion is a very primitive 
form of digestion and does not require 
an organized digestive system. Even in 
animals like sponges and coelenterates, 
the digestion is intracellular, though 
an alimentary canal like structure has 
developed in them. 

Extracellular digestion 

As animal body becomes more 
complex, digestive system has evolved 
to digest the food taken into the body. 
The digestive system in higher animal 
and man consists of alimentary canal and 
digestive glands that are specialized to 
produce digestive juices. Food is taken 
into alimentary canal and in the regions 
of digestion like mouth, stomach and 
duodenum, digestive juice is secreted by 
the digestive glands and the complex food 
swallowed is broken down to simpler food 
molecules by the action of enzymes of the 



ACTIVITY 6.2 



digestive juices. Since digestion takes place 
in the space or lumen of alimentary canal i.e 
outside the cell it is called as extracellular 
digestion -an advanced form of digestion. 

Digestion in human beings 

Food contains a number of nutrient 
molecules needed for building up of new 
body tissues, repairing damaged tissues 
and sustained chemical reactions. 



salivary glands 
pharynx 



gallbladdi 



pancrea: 

larga 
intestine 

small, 
intestine 

appendix- 




« 



^.T — rectun 




stomach 



Fig. 6.4 Human Digestive System 



Take I ml of starch solution (1%) into test tubes (A and B) 

Add I ml of saliva to test tube A and leave both the test tubes undisturbed for 
20-30 minutes 

Now add a few drops of dilute iodine to the test tubes 

In which test tube do you observe a colour change? 

What does this indicate about the presence or absence of starch in the two test tubes? 

What does this tell us about the action of saliva on starch? 

Is there a difference? If yes, in which case more energy from external sources is 
consumed. 



Food must be broken down to be 
used as a source of energy. The process 
of converting the complex food into a 
simple chemical substance, that can be 
absorbed and assimilated by the body is 
called digestion. The medical speciality 
that deals with the structure, function, 
diagnosis and treatment of diseases 
of stomach and intestine is called 
gastroenterology. 

The digestive system is composed of 
two groups of organs. They are 

1) The gastro intestinal tract 

2) Accessory digestive glands 

Digestion is brought about in a stepwise 
manner with the help of enzymes which 
are otherwise called bio-catalysts. 

The gastro intestinal tract (alimentary ca- 
nal) is a long muscular tube, about 9 mts in 
length and it commences from the mouth 
and ends in the anus. The mouth, buccal 
cavity, pharynx, oesophagus, stomach, 
small intestine, large intestine, rectum and 
anus are the parts of the alimentary canal. 

6.3. RESPIRATION IN PLANTS 

Why should we eat? 

Why should plants synthesize food? 

For the simple reason that all living 
organisms ranging from minute bacteria 
to large elephants, plants and humans, 
require energy for growth, movement and 
reproduction. 

Where does this energy come 
from? 

Food that we eat is the starch that is 
synthesized by plants and it is the source 
of energy. 



In fact, energy is locked up in food 
materials. During respiration, the food 
materials are oxidized (degraded). During 
this reaction, energy is released from the 
food and it is stored in a special chemical 
(or) biological substance called ATP 
(Adenosine triphosphate). 

The energy of ATP is utilized in various 
activities of cells. 

Apart from ATP, two other substances 
are also formed during respiration. They 
are CO^ and Hp. 



031:06^-602 
(Glucofie) 



-* 6CO2+6H3O+29OOKJ energy 
(ATP) 



Substance that is used in respiration 
is known as respiratory substrate. 
Respiratory substrates are of three kinds 
viz., carbohydrates, fats and proteins. 

Types of Respiration 

Depending on whether oxygen is used 
or not, respiration is of two types: 

1. Aerobic respiration. 

2. Anaerobic respiration. 

1. Aerobic respiration 

In majority of living organisms, oxygen 
is utilized during respiration. Respiration 
that uses oxygen is known as aerobic 
respiration. 

Aerobic respiration takes place in four stages: 

1. Glycolysis 

2. Oxidative decarboxylation of 
pyruric acid 

3. Kreb's cycle 

4. Electron transport chain. 



LIFE PROCESSES 



u 



In Glycolysis, glucose (a simple 
carbohydrate) is split into two molecules 
of pyruvic acid. This takes place in the 
cytoplasm, in a series of reactions and 
a number of enzymes are involved. With 
the formation of pyruvic acid, glycolysis 
comes to an end. 

Further oxidation of pyruvic acid takes 
place in the second and third stages 
occurring in the mitochondria. 

During the last stage i.e. electron 
transport chain, the energy associated with 
the liberated electrons is used to synthesize 
the ATP energy molecules at certain stages. 
Finally the hydrogen, an electron joins with 
oxygen to produce water as a by-product. 



Complete oxidation of a glucose 
molecule in aerobic respiration produces 
38 ATP molecules. 

2. Anaerobic respiration 

Insomeorganisms, oxygen is notutilized 
for respiration. This type of respiration is 
known as anaerobic respiration. It is also 
known as fermentation. 

[E.g. Conversion of milk into curd.] 

6.3. RESPIRATION IN ANIMALS 

Amoeba, Hydra, Sponge, etc,, live in 
water. In these organisms, respiration 
takes place through their body surface. 
Dissolved oxygen in water diffuses through 
the cell membrane or body surface into 



Absence of 
Oxygen 



Glucose 



In 
Cytoplasm 



( 6 - Carbon 
molecule ) 



Pyruvate 
(3 carbon 
molecule ) 

+ 
Energy 



(In Yeast) 



Lack of Oxygen 




_^Ethanol + Carbon-di-oxide + Energy 
( 2 - Carbon molecule ) 



Lactic acid + Energy 



( In our muscle cells ) ( 3-Carbon molecule ) 



Presence of 
Oxygen 



(In mitochondria) 
Fig. 6.5 Break down of glucose by various patliways 



_^Carbon-di-oxide + Water + Energy 



ACTIVITY 6.3 



Take some fruit juice or sugar solution and add some yeast to this. Take this 
mixture in a test tube fitted with a one-holed cork. 

Fit the cork with a bent glass tube. Dip the free end of the glass tube into the 
test tube containing freshly prepared lime water. 

What change is observed in the lime water and how long does it take for this 
change to occur? 

What does this tell us about the products of fermentation 



Lime Water Mr 




Ti ^Sugar + Water + Yeast 



Fig 6.6 Anaerobic respiration apparatus 

ATP 

ATP is the energy currency for the most cellular processes. The energy released 
during the process of respiration is used to make an ATP molecule from ADP 
and inorganic phosphate. 

Energy 



• ADP + Pi 



^ ATP 



• Think of how a battery can provide energy for many different kinds of uses. It 
can be used to obtain mechanical energy, light energy, electrical energy and 
so on. Similarly, ATP can be used in the cells for the contraction of muscles, 
protein synthesis, conduction of nervous impulses and many other activities. 



the cell and after its usage, the carbon-di- 
oxide produced is passively diffuses out 
into water. 

Repiratory surface for a fish is gill; for 
a frog it is lungs and skin the lungs for 
land vertebrates. 

Since the amount of dissolved oxygen 
is fairly low, compared to the amount of 
oxygen in the air, the rate of breathing in 
aquatic organisms is much faster than 
that seen in terrestrial organisms. Fishes 
take in water through their mouth and 
force it past the gills where the dissolved 
oxygen is taken up by the blood. 



Terrestrial organisms use the oxygen 
in the atmosphere for respiration. Oxygen 
is absorbed by different respiratory 
organs in different animals. All these 
organs have a structure that has bigger 
surface area, which is in contact with the 
oxygen-rich atmosphere. The exchange 
of oxygen and carbon-di-oxide has to 
take place across this surface. But it is 
usually placed within the body. So there 
are air passages present, that will take 
atmospheric air to this area. In addition, 
there is a mechanism for blowing the air 
in and out of this area where oxygen is 
absorbed. 



LIFE PROCESSES 



u 



In human beings, air is taken into the body 
through the nostrils. The air passing through 
the nostrils is filtered by fine hairs that line 
the passage. This passage is also lined with 
mucous which helps in this process. From 
here, the air passes through the throat into 
the lungs. Rings of cartilage are present in 
the throat which keep the air passage open 
and prevent it from collapsing. 

Within the lungs, the air passage 
branches repeatedly into smaller tubules 



Nasal cavity 

External nostril 

Pharynx 

Larynx 

Trachea 

Secondary 
bronchus 

Alveoli 
Diaphragm 



Fig. 6. 7 Human respiratory system 




ACTIVITY 6.4 



• Observe fishes in an aquarium, 
and their opening and closing 
of mouth and the gill slits (or the 
operculum which covers the gill slits) 
found behind their eyes also open 
and close. Is not the timing of the 
openings and closings of the mouth 
and gill slits co-ordinated? 

• Count the number of times the fish 
opens and closes its mouth in a 
minute. 

• Compare this into the number of 
times you breathe in and out in a 
minute. 



which finally terminate in balloon like 
structure called alveoli. The alveoli 
surrounded by blood capillaries provide 
a surface, where the exchange of gases 
takes place. 

6.4. TRANSPORTATION IN PLANTS 

We have discussed earlier, how the 
plants prepare food by the process 
of photosynthesis using various raw 
materials, like water, CO2, sunlight and 
chlorophyll. 

We already know that the chlorophyll 
pigments are in the leaf. So the leaf is the 
site for photosynthesis. The food prepared 
from the leaf should be transported to all 
other parts. 




Zone of maturation 



Root hair zone 



Zone of elongation 



Meriste ma tic region 



Fig. 6.8 Root liair region 

In the same manner, water is essential 
for photosynthesis and all other biological 
activities in the plants. For plants, soil is 
the nearest and richest source of water 
and other raw materials like nitrogen, 
phosphorus and other minerals. 



How do the absorbed water and 
minerals get transported from one place 
to all other parts of the plant body? 

Which part of the plant is in contact 
with the soil? 

For the above questions, you were 
getting answers already in your lower 
classes. 

The roots are the absorbing organs of 
the plant. 

Thus, plant transport systems will 
mobilize energy stores, (food) from 
leaves, and raw materials from roots. 
These two pathways are constructed 
as independently organized conducting 
tubes. 

i) Xylem transports water with 
dissolved minerals absorbed from 
the soil. 

ii) Phloem transports products of 
photosynthesis (food) from the 
leaves to the parts of the plant. 

Transport of water 

In xylem, vessels and tracheids are the 
conducting elements of the roots, stems 
and leaves. They are inter-connected 
to form a continuous system of water 
conducting channels, reaching all parts of 
the plant. In roots, the root hair cells in 
contact with the soil, actively take up ions. 




This creates a difference in the 
concentration of these ions between the 
root and the soil. Water, therefore enters 
into the root from the soil to eliminate this 
difference. 

This means that there is a steady 
movement of water into root xylem, 
creating a column of water that is steadily 
pushed upwards. 

Is this pressure enough to conduct 
water over the heights in tall and huge 
trees? 

Plants use another strategy to move 
water in the xylem upwards to the highest 
points of the plant body. This can be 
achieved by the process of transpiration, 
in which when the plant has an adequate 
supply of water. The water which is lost 



ater vapour 




+ Endodermis 



Fig. 6.9 Path of water across the root 



Fig. 6.10 Movement of water during 
transpiration in a tree 

through the stomata is replaced by water 
from the xylem vessels in the leaf. 

In fact, evaporation of water molecules 
from the cells of a leaf creates a suction 
which pulls water from the xylem cells of 
roots. 



LIFE PROCESSES 



u 



ACTIVITY 6.5 



Place a potted plant into a clear glass bell jar. The pot is covered with plastic 
to prevent water evaporating from the soil. 

Set up a second bell jar with a potted plant with leaves removed. 

Keep the bell jars in bright light at room temperature (20oC) for 6 hours. 

No liquid condenses in the bell jar without leaves. 

The bell jar containing the leafy plant has much more condensed liquid. 

Test the liquid it turns dry blue cobalt chloride paper to pink colour. Therefore 
the liquid is water. 

Discuss with your classmates, and find the reason why water droplets are 
formed in the potted plants containing leaves. 



The loss of water in the form of 
vapour from the aerial parts of the plant 
is known as transpiration. 

Thus, transpiration helps in the 
absorption and upward movement of 
water and mineral dissolved in it from 
roots to the leaves. It also helps in 
temperature regulation. The effect of 
root pressure in transport of water is 
more important at night. During the 
day when the stomata are open, the 
transpiration pull becomes the major 
driving force in the movement of water 
in the xylem. 

Transport of food and other 
substances 

How are the products of photosynthesis 
transported from leaves to other parts 
of the plant? 

The transport of soluble products of 
photosynthesis is called translocation 
and it occurs in the part of the vascular 
tissue known as phloem. Besides 
the products of photosynthesis, the 



phloem transports amino acids and 
other substances. These substances 
are especially delivered to the storage 
organs of roots, fruits, seeds and to 
growing organs. The translocation of 
food and other substances takes place 
in the sieve tubes (sieve tubes are 
one of the constituents of the phloem 
which act as pipe line from leaves 
to the other parts of the plant) with 
the help of companion cells both in 
upward and downward directions. The 
translocation by phloem is achieved by 
utilizing energy. Materials like sucrose 
is transferred into phloem tissue using 
energy from ATP. This increases the 
osmotic pressure in the tissue causing 
water movement. This pressure moves 
the material in the phloem to tissues 
which have less pressure. This allows 
the phloem to move material according 
to the plant's needs. For example, in 
the spring, sugar stored in root or stem 
tissue would be transported to the buds, 
which need energy to grow. 



Questions 

1. What are the components of 
the transport system in highly 
organized plants? 

2. How are water and minerals get 
transported in plants? 

3. How is food transported in 
plants? 

Transportation in animals 

In microscopic organisms such as 
Amoeba and Paramecium, the volume of 
body is so small that useful substances 
can be distributed by a process called 
diffusion. Oxygen for example, enters an 
amoeba through the cell membrane and 
spreads out i.e diffuses, in all directions at 
the rate approximately equal to the rate at 
which oxygen is consumed in respiration. 
Similarly, carbon-di-oxide diffuses out 
of an Amoeba with sufficient speed to 
prevent it accumulating to harmful levels 
within the cell. 

In large multi-cellular organisms, 
however, the body volume is so great that 
diffusion alone is far too slow a process 
for adequate distribution of oxygen and 
food, and removal of waste. 

The cells in the multi-cellular 
organisms relying on diffusion alone 



ACTIVITY 6.6 



would be a tightly packed crowd. 
Those in the middle region would not 
get enough oxygen. Hence, most large 
organisms do not rely on diffusion for 
their supply of food and oxygen. They 
have a transport system of some kind to 
carry these substances to all the cells in 
the body. 

In human body, for example the 
transport system consists of a pump 
called heart which propels the fluid called 
blood around a complex system of tubes 
called blood vessels. As it passes through 
these blood vessels, the blood picks up 
oxygen from the lungs and transport it to 
every cell in the body. Blood also picks 
up waste product such as carbon-dioxide 
and many other substances like salts from 
the cells and excrete out from the body. 

Lymph 

There is another type of fluid which 
is also involved in transportation. This is 
called lymph or tissue fluid. It is similar to 
the plasma of blood but it is colourless 
and contains less protein. Lymph drains 
into lymphatic capillaries from the 
intercellular spaces, which join to form 
large lymph vessels that finally open 
into veins. Lymph carries digested and 
absorbed fat, from intestine and drains 
excess fluid from extra cellular space 
back into the blood. 



1. Visit a health centre in your locality and find out what is the nornnal 
range of haemoglobin content in human beings. 

2. Is it the same for children, women and men? Discuss why does the 
difference exist? 



LIFE PROCESSES 



u 



6.5. EXCRETION IN PLANTS 

What is excretion? 

How does the excretion take place in 
plants? 

Excretion is the process by which the 
metabolic waste products are removed 
from the plant body. 

In plants there are different ways for 
excretion. 

1. Plant waste products are stored in 
cellular vacuoles. 

2. Waste products may be stored in 
leaves that fall off. 

3. Other waste products are stored as 



resins and gums, especially in old 
xylem tissues. 

4. Plants also excrete some waste 
substances into the soil around 
them. 

Excretion in animals 

In unicellular protozoans, the excreta are 
discharged out through the contractile- 
vacuoles, which are formed by the 
absorption of water and other excreta. 

In coelenterates and sponges, 
the excreta diffuse out through the cell 
membrane. 

In flat worms and round worms, the 
excretory tubes develop for transporting 



Artificial i^idney (Hemodialysis) 



Kidneys are vital organs for survival. Several factors like infections, injury or restricted 
blood flow to kidneys reduce the activity of kidneys, This leads to accumulation of 
poisonous wastes in the body, which can even lead to death. In case of kidney failure, 
an artificial kidney can be used. An artificial kidney is a device to remove nitrogenous 
waste products from the blood through dialysis. 



Line from artery 
to pump 



Tubling made 
of a selectively 
permeable 
membrane 




.ine from 

apparatus 

to vein 



t t 1^ 



Fresh dialysing 
solution 



used 
dialysirig 
solution (With 
urea and 
excess salt 



Artificial kidneys contain a number of tubes 
with a semipermeable lining, suspended in a 
tank filled with dialysing fluid. This fluid has the 
same osmotic pressure as blood, except that it 
is devoid of nitrogenous wastes. The patient's 
blood is passed through these tubes. During 
this passage, the waste products from the 
blood pass into dialysing fiuid by diffusion. The 
purified blood is pumped back in to the patient. 
This is similar to the function of the kidney, but 
it is different since there is no re- absorption 
involved. Normally, in a healthy adult, the 
initial filtrate in the kidneys is about 180 L daily. 
However, the volume actually excreted is only 
a litre or two a day, because the remaining 
filtrate is re- absorbed in the kidney tubules. 



the excreta to exterior. In annelids special 
kidneys called nephridia are evolved to 
collect excreta from the coelomic cavity. 

In vertebrates, an elaborate well- 
defined excretory system has developed 
with kidneys and excretory tubes. The 
kidney of vertebrates consists of nephrons 
which filter the blood and form the urine 
and large amount of ammonia is found in 
fish excreta. They are called ammoniatelic 
animals. The birds are called uricotelic 
animals as their excretory substance 
is composed mostly of uric acids. In 
mammals urea is the main excretory 
products so they are called ureotelic 
animals. 

Nephron 

Each Nephron consists of a filtering 
apparatus called glomerulus and uriniferous 
tubules.The glomerulus filters the plasma 
part of the blood to form urine. The urini- 
ferous tubules reabsorb the substances 
required in the body from that filterate and 
the final urine product contains mostly 
water and nitrogenous waste products. 

6.6. NERVOUS SYSTEM 

The millions of cells and the scores of 
different tissues and organs in the body 
of an animal do not work independently 
of each other. Their activities are 
co-ordinated. This means that they work 
together, performing the various functions at 
certain times and at certain rates according 
to the needs of the body as a whole. 

One of the most familiar examples of 
co-ordination is the way in which muscles 
works together during movement. When 
a boy runs to catch a ball, for example, he 
uses hundreds of muscles to move the 



joints in his arms, legs and back using 
informations from his sense organs. 
The boy's nervous system co-ordinates 
these muscles so that they contract 
in correct sequence with the correct 
degree of power, and for precisely the 
correct length of time needed to get him 
to the spot where he can catch the ball. 
Muscular activities like running to catch 
a ball, involves many other forms of 
co-ordination, such as those which 
increase the rate of breathing and heart 
beat to adjust blood pressure, remove 
extra heat from body and maintaining 
sugar and salt levels in the blood. 
Furthermore, all these co-ordinations 
occur as an unconscious process. 

Worms have the simplest form of 
coordinating system where an earthworm 
has dual nerve cords. Two ganglia acts 
as brain and eye spots act as photo 
receptors. 

In insects, ganglia are connected by 
a ventral nerve cord function as brain. 
Well-developed sensory organ for vision 
and antennae for olfactory function are 
present. 

In mammals and other well-developed 
vertebrates this co-ordination is achieved 
by nervous system and endocrine system. 

In simple, the nervous system consists 
of tissues which conducts "messages" 
called nerve impulses, at a high speed to 
and from all parts of the body. 

6.7. CO-ORDINATION IN PLANTS 

How do plants co-ordinate? 

Unlike animals, plants have neither 
nervous systems nor muscles. 



LIFE PROCESSES 



u 




Fig. 6.11 Sensitive Plant (Touch-me-not plant) 



So, how do they respond to stimuli? 

When we touch the leaves of Touch- 
me-not plant, they begin to fold up and droop. 

When a seed germinates, the roots go 
down , the stem comes up above the soil. 

What happens during the above actions? 

In the first instance, the leaves of 
sensitive 

Plants show two different types of 
movements. 

1. Movement independent of growth 

2. Movement dependent on growth 

Movement- Independent of growth 

Immediate response to stimulus 

This movement is sensitive to plant. 
Here, no growth is involved but, the plant 
actually moves its leaves in response to 
touch. But there is neither nervous tissue 
nor muscle tissue. 

How does the plant detect the touch 
and how do the leaves move in response? 

In touch-me-not plant, if we touch at 
one point, all the leaflets show the folding 
movements. This indicates that the 
stimulus at one point is communicated. 
But unlike in animal, there is no specialized 



tissue in plants for transmitting the 
information. Plant cells change the shape 
by changing the amount of water in them 
resulting in swelling or shrinking and 
therefore the leaves in touch-me-not plant 
shrinks. 

Movement dependent on growth: 

More commonly, the plants respond to 
stimuli slowly by growing in a particular 
direction. Because thisgrowthisdirectional, 
it appears as if the plant is moving. 

Let us understand this type of 
movement with the help of some 
examples. 

1. Response of the plant to the 
direction of light (Phototropism) 

2. Response of the plant to the 
direction of gravitational force 
(Geotropism) 



ACTIVITY 6.7 ^H 


1 . Go to the field and find the 


touch-me-not plant. 


2. Touch the plant at one 


point. 


3. Observe what happens. 



3. Response to the direction of water 
(Hydrotropism) 

4. Response to the direction of 
chemicals (Chemotropism) 

Phototropism 

It is the growth of the stem towards 
the direction of sunlight. 




Negatively 
geotropic 




Positively '^ 
geotropic 



Fig 6.13 Geotropism 

Hydrotropism 

The roots of very huge trees grow 
towards the availability of water source 

(e.g) The roots of coconut tree are seen 
away from the plant for the want of water. 

Chemotropism 

This is the movement of plant parts 
towards the direction of chemicals, (e.g) 
The pollen tubes grow towards ovule. 



Fig. 6.12 Pliototropism 
Geotropism 

It is the growth of roots towards the 
direction of gravitational force. 

Roots cannot grow towards sunlight 
and stem cannot grow towards 
gravitational force. 



ACTIVITY 6.8 



Fill a conical flask with water. 

Cover the neck of the flask with a wire mesh. 

Keep two or three freshly germinated bean seeds on the wire mesh. 

Take a cardboard box which is open from the side. 

Keep the flask in the box in such a manner that the open side of the box faces 
light, coming from a window. 

After two or three days, you will notice that the shoots bend towards light and 
roots away from light. 

Now turn the flask so that shoots are away from the light and roots towards 
light. Leave it undisturbed in this condition for a few days. 

Have the old parts of the shoot and root changed direction? 

Are there differences in the direction of the new growth? 

What do you understand from this activity? 



LIFE PROCESSES 



u 



6.9. HORMONES IN ANIMALS 

The endocrine system consists of 
ductless glands and their secretions 
called hormones. Hormones are bio - 
chemical substances which act as bio 
catalysts speeding up the chemical 



reactions. These are released into the 
blood stream and transported around 
the body. Harmones co-ordinate the 
physiological activities in our body. A 
detailed account on hormones is dealt in 
chapter 3. 



EVALUATION 



PART A 

1. In monotropa the special type of 
root which absorbs nourishment is 
(Haustoria, Mycorrhizal root, Clinging 
root, Adventious root) 

2. The product obtained in the Anaerobic 
respiration of yeast is (Lactic acid. 
Pyruvic acid, Ethanol, Acetic acid) 

3. The roots of coconut tree are seen 
away from the plant. Such kind of 
movement of root for want of water is 
(Phototropism,Geotropism,Chemo-tro- 
pism, Hydrotropism) 

4. The xylem in the plants are responsi- 
ble for (transport of water, transport of 
food, transport of amino acid, trans- 
port of oxygen) 

5. The autrotropic nutrition requires (CO2 
and water, chlorophyll, sunlight, all the 
above) 

PARTE 

6. Name the types of vascular tissues in 
the plant stem which are labelled as A 
and B 




a) Name A and B 

b) What are the materials 
transported through A? 

c) What are the materials 
transported through B? 

d) How do the materials in A move 
upwards to leaves? 




7. Observe the above diagram 

a) Mention the type of movements 
shown in fig, A and B. 

b) How does the movement differ from 
the movement of mimosa 

8. Match the methods of nutrition of 
special organs with suitable examples. 



Autotrophs 


Mycorrhiza 


Cuscutta 


Parasites 


chlorophyll 


Monotropa 


Saprophytes 


Haustoria 


Hibiscus 



IS 



9. In the process of respiration 

carbon compound, the lactic is 

carbon compound. 

10. Sugar is converted into alcohol. From 
the above statement what kind of 
process takes place? Which micro 
organism is involved? 

11. Pick out the odd one : The parts 
of the alimentary canal are 
( Pharynx, mouth, buccal cavity, 
pancreas) 

12. In human beings air enters into the 

body through and moves 

into In fishes water enters 



into the body through 



and 



the dissolved oxygen of water diffuses 
into 



PARTC 



13. Compare the respiration in higher 
plants with the respiration in lower 
plants 

14. Is the pressure created in xylem 
enough to conduct water in tall trees. 
Give reasons. 

15. In touch me not plant the leaves show 
movements. What type of movement 
have you observed. Discuss. 



NAME OF THE PLANTS IN ENGLISH & TAMIL ^ 


L 






1 




^Jjffl^^ 




^ 


pW IT IS 

CALLED 

.OCALLY 


1 


MONOTROPA 
UNIFLORA 


INDIAN PIPE 


IDTSeSITl^SjTUT 




2 


VISCUM 


PARASITIC 
PLANT 


l_|SOg}|(l55251 




3 


CUSCUTA 
REFLEXA 


PODDERPLANT 


/ffL^Tlfl 





FURTHER REFERENCE 

Books : 1. Modern Plant Physiology Sinha Narosa 

2. Fundamentals of plant physiology Jain .V.K. 



Chapter 






CONSERVATION OF 
ENVIRONMENT 




.Conservation of Environment 



Living organisms live in different 
surroundings. Some plants and animals 
completely live in water and some others 
live on land. 

Man also leads life in different 
surroundings. Some live in cities, some in 
towns and some in villages. How do they 
adapt themselves to the place they live in? 

Plants, animals, human beings survive 
with the interaction between them and the 
non-living things like air, water and land. 
Human beings depend on the resources of 
nature. These resources include soil, water, 
coal, electricity, oil, gas, etc. These resources 
improve the life style of human beings. 



Environmental science can be 
defined as the study of organisms in 
relation to their surrounding. 

In the course of development, 
unplanned and vast misuse of natural 
resources like water, forest produce, land 
and mineral resources have occurred. 
This has led to an imbalance in nature 
and release of many harmful substances 
in the atmosphere. 

Mankind is greatly influenced by the 
surrounding in view of the problem of 
over Population, environmental pollution, 
human survival, pest control and 
conservation of natural resources. 




Living Environment 

Plants 



Living Environment 

Animals 



\ 



NON Living Environment 

Land, Water, Air,Minerals 




Fig. 7.1 Interaction between non-living and living components in the biosphere 



CONSERVATION OF ENVIRONMENT 



U 



In our daily activities, we generate a lot 
of materials that we throw away. 

• What are some of these waste materials? 

• What happens after we throw them away? 

Human activities related to livelihood 
and welfare generate waste. All wastes 
are pollutants and they create pollution 
in one way or another. Air, land and 
water surroundings are affected due to 
improper disposal of wastes which create 
an imbalance in the environment. 

• What is Pollution? 

• What are Pollutants? 

Pollution: Any undesirable change 
in the physical, chemical or biological 
characteristics of air, land and water that 
affect human life adversely is called pollution. 

Pollutant: Asubstance released into the 
environment due to natural or human activity 
which affects adversely the environment 
is called pollutant, e.g. Sulphur-di-oxide, 
carbon-monoxide, lead, mercury, etc. 

7-1-CLASSIFICATION OF 
WASTES 

1. Bio-degradable wastes 

2. Non-bio-degradable wastes 

Substances that are broken down 
by biological process of biological or 
microbial action are called bio-degradable 
waste, e.g. wood, paper and leather. 

Substances that are not broken down 
by biological or microbial action are called 
non-bio-degradable wastes, e.g. Plastic 
substances and mineral wastes. 

How to protect us from these hazardous 
wastes ? 

Why do the government and so many 
organizations conduct awareness 



ACTIVITY 7.1 



Find out what happens to the waste 
generated at home. Is there a system 
in place to collect this waste? 

Find out how the local body (panchayat, 
municipal corporation or resident 
welfare association) deals with the 
waste. Are there mechanisms in place 
to treat the bio-degradable and non- 
bio-degradable wastes separately? 
Calculate how much waste is generated 
at home in a day. 

How much of this waste is bio- 
degradable? 

Calculate how much waste is 
generated in the class room in a day. 

How much of this waste is non bio- 
degradable? 

Suggest ways of dealing with this 
waste 



THINK IT OVER 



Disposable cups in trains 

If you ask your parents, they will probably 
remember a time when tea in trains was 
served in plastic tumblers which had to be 
returned to the vendor. The introduction 
of disposable cups was hailed as a step 
forward for reasons of hygiene. No one at 
that time probably thought about the impact 
caused by the disposal of millions of these 
cups on a daily basis. Some time back, 
Kulhads, that is, disposable cups made 
of clay, were suggested as an alternative. 
But a little thought showed that making 
these Kulhads on a large scale would 
result in the loss of the fertile top-soil. Now 
disposable paper-cups are being used. 
What do you think are the advantages of 
disposable paper-cups over disposable 
plastic cups? 



Progarmmes against using plastics ? 

The following methods are adopted for 
the disposal of harmful waste materials. 

1. Land Fills 

There are permanent storage facilities 
in secured lands for military related liquid 
and radioactive waste materials. High 
level radioactive wastes are stored in 
deep underground storage. 

2. Deep well injection 

It involves drilling a well into dry 
porous material below ground water. 
Hazardous waste liquids are pumped 
into the well. They are soaked into the 
porous material and made to remain 
isolated indefinitely. 

3. Incineration 

The burning of materials is called 
incineration. 

Hazardous bio-medical wastes 
are usually disposed off by means of 
incineration. Human anatomical wastes, 
discarded medicines, toxic drugs, blood, 
pus, animal wastes, microbiological and 
bio-technological wastes etc., are called 
bio-medical wastes. 

Management of non-hazardous 
wastes - solid waste 
nrianagement 

Reuse and recycling technique 

The separating out of materials such 
as rubber, glass, paper and scrap metal 
from refuse and reprocessing them for 
reuse is named as reclamation of waste or 
recycling. 



Paper 

(54% recovery) Can be repulped 
and reprocessed into recycled paper, 
cardboard and other products. 

Glass 

(20% recovery) Can be crushed, re- 
melted and made into new containers or 
crushes used as a substitute for gravel 
or sand in construction materials such 
as concrete and asphalt. Food waste 
and yard wastes (leaves, grass etc.,) can 
be composted to produce humus soil 
conditioner. 

7.2. WATER MANAGEMENT 

Due to increasing demands for water 
and reduced availability of fresh ground 
water resources, urgent measures have 
to be taken to conserve each and every 
drop of water that is available. 

Clean and fresh water is essential for 
nearly every human activity. Perhaps 
more than any other environmental 
factors, the availability of water 
determines the location and activities of 
human beings. 

Can you list out the reasons for 
increasing demand of water? 

7.2.1. Sources of water 

Water is a basic natural resource 
and valuable asset to all nations. 
Human beings depend on water for all 
their needs such as bathing, washing, 
cooking, transportation and power. 
Water in India is of two kinds. Salt 
water and fresh water. Fresh water is 
obtained from rain water, surface water 
and ground water. 



CONSERVATION OF ENVIRONMENT 



U 



The main sources of water are rain and snow 
which form a part of the hydrological cycle. 

Surface water 

India is blessed with a number of rivers, 
lakes, streams and ponds. 

Ground water 

Aquifers are under ground reserves of 
fresh water. 

In the water table, water that percolates 
into the ground through porous rocks is 
ground water. These porous rocks are 
saturated with water to a certain level. The 
upper layer of waterlevel is the watertable. 
The ground water is important for plant 
growth, man also taps this water through 
tube wells and bore wells. Scanty rainfall 
and unnecessary felling of trees affect 
the ground water level. 

7.2.2. Fresh water management 

To meet out the water scarcity we need 
several ways to increase the water supply. 

i) Seeding clouds 

Seeding clouds with dry ice or potassium 
iodide particles sometimes can initiate rain 
if water laden clouds and conditions that 
favour precipitation are present. 

ii) Desalination: (Reverse osmosis) 

Desalination of ocean water is a 
technology that has great potential for 
increasing fresh water. Desalination is 
more expensive than most other sources 
of fresh water. In desalination, the 
common methods of evaporation and re- 
condensation are involved. 

iii) Dams, reservoirs and canals 

Dams and storage reservoirs tap run- 
off water in them and transfer the water 



from of excess to areas of deficit using 
canals and underground pipes. 

iv) Water shed management 

The management of rainfall and 
resultant run-off is called water shed 
management. Water shed is an area 
characterized by construction of small 
dams to hold back water which will provide 
useful wildlife habitat and stock watering 
facilities. 

v) Rain water harvesting 

Rain water harvesting essentially 
means collecting rain water from the roof of 
building or courtyards and storing it under 
ground for later use. The main idea in 
harvesting rain water is to check the run-off 
water. The rain water that falls on the roofs 
of buildings or in courtyards is collected 
through pipes and stored in under ground 
tanks of the buildings fitted with motor for 




Rainwater 
aquifier 



Fig. 7.2 Rain water liarvesting 

lifting water for use. The process of rain 
water harvesting is not only simple but 
also economically beneficial. It helps in 
meeting the increased demand for water, 
particularly in urban areas and prevent 
flooding of living areas. 

vi) Wetland conservation 

It preserves natural water storage and 
acts as aquifer recharge zones. 



vii) Domestic conservation 

As an individual, every one can reduce 
the water loss by taking shower, using 
low-flow taps, using recycled water for 
lawns, home gardens, vehicle washing 
and using water conserving appliances. 

viii) Industrial conservation 

Cooling water can be recharged and 
waste water can be treated and reused. 




Fig. 7.3 Domestic conservation 
method of water 

7.3. WILDLIFE SANCTUARIES 

Wildlife 

All non-domesticated and non- 
cultivated biota found in natural habitat 
are termed 'wildlife'. It includes all the 
natural flora and fauna of a geographic 
region. Wildlife is an asset to be protected 
and preserved to our own advantage and 
to the benefit of future generations. 

There are approximately 400 
varieties of reptiles, 200 varieties 
of amphibians, 3000 varieties 
of fishes, 3000 species of birds 
20,000 species of flowering 
plants and 4100 species of 
mammals found in our country 
according to the latest census 
estimate. 



It is essential to protect and conserve 
wildlife because they have aesthetic, 
ecological, educational, historical and 
scientific values, a good biotic diversity 
is essential for ecological balance. Large 
scale destruction of wildlife could lead to 
ecological imbalance. Wildlife also adds 
aesthetic value and from this, eco-tourism 
is being promoted in a big way by several 
countries. Wildlife and their products 
could be of great economic value if utilized 
properly. The invulnerable plants could 
yield products of immense medicinal 
value in future. Wildlife also forms as 
store of vast genetic diversity which could 
be properly used with advances in genetic 
engineering. Thus wildlife has been of 
great value in the past and will continue 
to be so in the future. Protection and 
conservation of wildlife, therefore gains 
importance. 

SANCTUARIES 

Wildlife sanctuary is an area constituted 
by competent authority in which hunting or 
capturing of animals is prohibited except 
by or under control of the highest authority 
responsible for management of the area. 

Wildlife sanctuaries were established 
in India in the pursuit of conserving wildlife 
which was suffering due to ecological 
imbalance caused by human activities. 
There are 89 National parks, 500 wildlife 
sanctuaries, 27 Tiger reserves, 200 Zoos 
and 13 Biosphere reserves in the country 
covering an area of 1.6 lakh sq.km. 

7.4. BALANCE IN ECOSYSTEM 
What is Ecosystem? 

• Fish lives in Water. 

• Tiger lives in Forest. 



CONSERVATION OF ENVIRONMENT 



U 



Important sanctuaries in Tamilnadu 



L 


tSTiRt 


'mnftif 


Indira Gandhi Wildlife, 
Sanctuary 


Western Ghats. 


Tiger, leopard, porcupine, 
nilgiris tahr, civet cat, 
elephant, gaur, pangolin. 


Kalakkadu Wildlife 
Sanctuary. 


Tirunelveli District 


Lion tailed macaque, 
sambhar, sloth bear, gaur, 
flying squirrel. 


Srivilipathur Grizzled 
squirrel wildlife Sanctuary 


Virudhunagar District 


Grizzled squirrels, mouse 
deer, barking deer, tree 
shrew. 


Vedathangal Bird's 
Sanctuaries 


Kancheepuram District 


Cormorants, egrets, grey 
heron, open-billed stork, 
white bears, shovellers, 
pintails, stets, sandpipers. 


Mudumalai wildlife 
Sanctuary 


The Nilgiris 


Elephants, gaur, langur, 
tigers, leopards, sloth bear, 
sambhar, wildbear, jackal, 
porcupine, mangoose. 


Viralimalai 


Trichy District 


Wild peacocks 


Gulf of Mannar marine 
National Park. 


Coast of Rammad and 
Tuticorin district. 


Coral reefs, dugong, tuties, 
dolphins, balanoglossus. 


Mundhanthurai wildlife 
Sanctuary. 


Tirunelvelli District 


Tiger, bonnet macaque, 
langurs, sloth bear, wild 
dog. 


Vallanudu Blackbuck 
Sanctuary. 


Tuticorin District 


Blackbuck, jungle cat, hare, 
mongoose. 


Arignar Anna Zoological 
Park 


Vandalur 


Lion, elephant, tiger, 
monkeys. 


Mukkurthi National Park 


The Nilgiris 


Tigers. 


Point calimere wildlife 
Sanctuary 


Nagapattinam district 


Chital, wild bear, plovers, 
stilts, bonnet macaque. 


Anamalai wildlife sanctuary 


Slopes of western ghats. 


Civet cat, porcupine, gaur, 
tiger leopard, nilgiri tahr. 



Important National Parks, wildlife sanctuaries and reserves. 



Bandhipur National Park 
(It is a tiger reserve too) 


Karnataka 


Indian bison, chital, sloth 
bear, elephants. 


Corbett National Park 
(India's first national park) 
(Tiger reserve too) 


Uttaranchal 


Tigers, chital, elephants, 
leopard. Jungle cat and 
sloth bear. 


Gir National Park 


Gujarat 


Asiatic Lion 


Kanha National Park 
(Tiger reserve) 


Madhyapradesh 


Deer Tiger, Wilddog, 
chital. 


Bharathpur Bird sanctuary 


Rajasthan 


374specialof bird, e.g. 
Indian darters, spoonbills, 
painted stock, open billed 
stork, black necked stork 
etc,. 


Manas wildlife sanctuary 
(Tiger reserve) 


Assam 


Hispid hare (rere), pygmy 
hog, golden langue 


Sunderbans National Park 
(Tiger reserve) 


West Bengal 


Unique Royal Bengal 
Tigers. 



How can they lead their life in the 
above habitats? 

A community of organisms that interact 
with one another and with the environment 
is called an ecosystem. 

The Ecosystem is of two types, namely 
aquatic and terrestrial. 

What are the major components in 
Ecosystem? 

There are four major components, namely: 

1. Abiotic factors 

2. Producers 

3. Consumers 

4. Decomposers. 



Producers, consumers 
decomposers are biotic factors. 



and 



Pond Ecosystem 

An example for aquatic ecosystem is 
a pond. 

Abiotic factors 

It includes light, temperature, hydrogen 
ion concentration, inorganic substances 



like CO,, H,, O,, N, PC,, 



CO3 and S and 



organic substances like carbohydrates, 
proteins and lipids. 

Biotic factors 

It includes producers and consumers. 
Producers are the water living plants 
like Hydrilla, Valllsneria etc., and 
phytoplankton like Chlamydomonas, 
Vol vox and Spirogyra. 



CONSERVATION OF ENVIRONMENT 



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Primary consumers or herbivores 

Zooplanktons like insects, larvae of 
Dragon-fly consume the phytoplanktons. 

Secondary Consumers 

These are certain fishes, frogs, water 
beetles etc., which feed on the primary 
consumers in the pond. 

Tertiary Consumers 

These are big fishes and kingfisher that 
feed on small fishes. 

Decomposers 

Several bacteria and fungi form the 
decomposers in the pond. 



TOP CARNIVORES 



T 



CARNIVORES 



I 



HERBIVORES 



PRODUCERS 



SUNLIGHT 



ACTIVITY 7.2 



• While creating an aquarium did 
you take care not to put an aquatic 
animal which would eat others? 
What would happen otherwise? 

• Make groups and discuss how each 
of the above groups of organisms 
are dependent on each other. 

• Write the aquatic organisms in 
order of who eats whom and form a 
chain of at least three steps. 

• Would you consider any one group 
of organisms to be of primary 
importance? Why or why not? 



An ecosystem is maintained by the 
balance in nature such as the balance 
between hawks and mice, if hawk 
population is larger than the mice 
population, then it is not balanced. 

They are balanced between resources 
like a banana tree and monkeys. If the 
banana trees stop growing, the monkeys 
won't get bananas. 

An ecosystem maintains the balance 
between the number of resources and the 
number of users or the balance between 
prey and predators. 

What is food chain and food 
web? 



Fig. 7.4 Flow of energy in an ecosystem 
BALANCE IN ECO-SYSTEM 



Various organisms are linked by food 
chains in which the food energy is passed 
from one organism to another in a linear 
A balanced ecosystem is an ecological fashion, 
community together with its environment 



and functioning as a complex unit. 



e.g. Food chain of a grassland ecosystem. 



Grass -^ Grass hopper -^ Frog -^ Snake^Eagle 

(Producers) (Herbivores) (Primary (Secondar (Teritary 
consumer) consumer) consumer) 

Fig. 7.5 Grassland ecosystem 



ACTIVITY 7.3 



• Go to a pond and observe the 
organisms that lives in the pond. 

• List out the organisms. 

• Prepare a chart of food chains 



Food Web 

The food chains are interlinked to form 
food webs, So every component of the 
ecosystem is connected to one another. 

How is the ecosystem maintained? 

There are many factors which maintain 
the harmony in an ecosystem naturally. 
Disturbing any one factor could have a 
drastic impact upon the living conditions 
of other organisms that will result in an 
imbalance. For example, removal of trees 
and vegetation would affect both land and 
water ecosystems as there will be no 
food for organisms. Killing animals and 
polluting land, air and water also disturb 
the balance in nature. 

Inorder to maintain the eco-balance in 
an ecosystem, there should be recycling 
of nutrients, minerals, and water. Careful 
use of natural resources will maintain 
the eco-balance. Thus eco-balance or 
ecological balance is the maintenance of 







Fig. 7.6 Food web 
balance between living components and 
its resources of an ecosystem, so that it 
remains a stable environment community 
for the better functioning of the organisms. 

Bio - Geo chennical cycles 

In an ecosystem, the energy from 
the sun is fixed by the plants. Then it is 
transferred to herbivores and carnivores, 
i.e. the energy flows in one direction 
only. But the minerals required in the 
ecosystem are continuously absorbed 
by the plants and transferred to animals. 
As the minerals are removed from the 
soil, they have to be replaced or cycled. 
These minerals are returned to the soil by 
the decomposition of dead and decaying 
materials by saprophytic organisms such 
as bacteria and fungi (You have studied 
the cycles in earlier classes in detail.) 

7.5. COAL AND PETROLEUM 

7.5.1 Coal 

Coal is a compost primarily of carbon 
along with variable quantities of other 
elements chiefly sulphur, hydrogen, 
oxygen and nitrogen. 



CONSERVATION OF ENVIRONMENT 



U 



Coal is a fossil fuel and is the largest 
source of energy for the generation of 
electricity world wide, as well as one of 
the largest worldwide sources of CO2 
emissions. Gross CO2 emission from coal 
usage is high and more than those from 
petroleum and about double the amount 
from natural gas. 




Fig. 7.7 Coal 

Coal is obtained through mining or in 
open pits. Coal is primarily used as a 
solid fuel to produce electricity and heat 
through combustion. When coal is heated 
in air, coal burns and produces mainly 
carbon-di-oxide gas. Coal is processed 
in industry to get some useful products 
such as coke, coal tar and coal gas. 

Environnnental effects of coal 
burning 

1. Generation of waste products which 
contain mercury, uranium, thorium, 
arsenic and other heavy metals, 
which are harmful to human health 
and environment. 



5. 
6. 



Sulphur particles present in the 
coal will cause acid rain.. 

Interference with ground water and 
water table levels. 

Contamination of land and water 
ways. 

Dust nuisance. 

Release of CO2, a green house 
gas, which causes climate change 
and global warming. 



7. Coal is the largest contributor to 
the man-made increase of CO2 in 
the air. 



ACTIVITY 7.4 



Visit Neyveli lignite corporation. 

See how the coal is mined. 

Discuss with your classmates 
about the uses of coal. 



7.5.2 Petroleunn 

In modern life today, we are 
inseparable from petrol and petroleum 
products. Petroleum or crude oil is a 
naturally occurring, toxic, flammable 
liquid consisting of a complex mixture 
of hydrocarbons and other organic 
compounds that are found beneath the 
earth's surface. 

Do you know how does petroleum 
form? 

Petroleum was formed from organisms 
living in the sea. After the death of those 
organisms, their bodies settled at the 
bottom of the sea and were covered with 
layers of sand and clay. Over millions of 



years, absence of air, high temperature 
and high pressure transformed the dead 
organisms into petroleum and natural 
gas. 

Many useful substances are obtained 
from petroleum and natural gas. These 
are used in the manufacture of detergents, 
fibers (polyester, nylon, acrylic etc.), 
polythene and other plastic substances. 
Hydrogen gas, obtained from natural 
gas, is used in the production of fertilizers 
(urea). Due to its great commercial 
importance, petroleum is also called 
'Black Gold'. 

Environmental effects 

Oil Spills 

1. Crude oil (refined fuel) spills from 
tanker ship and accidents have 
damaged natural ecosystem. 

2. Oil Spills at sea are generally 
causing more damage than those 
on land. This can kill sea birds, 
mammals, shellfish and other 
organisms, because of their lateral 
spreading on water surface. 

Tar Balls 

A tar ball is a blob of oil which has been 
weathered after floating on the ocean. Tar 
balls are aquatic pollutants in most of the 
seas. 




Alternatives to petroleum - based 
vehicle fuels 

1. Internal combustion engines 
(Biofuel or combustion hydrogen) 

2. Electricity (for e.g. all electric (or) 
hybrid vehicles), Compressed air 
or fuel cells (hydrogen fuel cells). 

3. Compressed natural gas used by 
natural gas vehicles. 

7.6 GREEN CHEMISTRY 

Green chemistry is the design of 
chemical products and processes to 
reduce or eliminate the use and generation 
of hazardous substances. 

The concept of green chemistry was 
introduced in 1995. The Green Chemistry 
Institute was recently created and the 
Presidential Green Chemistry challenge 
awards were established in 1999. 



MORE TO KNOW 



Many countries are making 
commitments to lower green house 
gas emissions according to the 
Kyoto protocol. 



ACTIVITY 7.5 



Coal is used in thermal power stations 
and petroleum products like petrol 
and diesel are used in means of 
transport like motor vehicles, ships 
and aeroplanes. We cannot really 
imagine life without a number of 
electrical appliances and constant use 
of transportation. So, can you think of 
ways in which consumption of coal and 
petroleum products can be reduced? 



Fig 7.8 Petroleum Industry 



CONSERVATION OF ENVIRONMENT 



U 



• Greener reaction conditions for an 
old synthesis e.g. replacement of 
an organic solvent with water or the 
use of no solvent at all) 

• A greener synthesis for an old 
chemical (e.g. asynthesis which uses 
biomass rather than petrochemical 
feed stock or the use of catalytic 
rather than stoichiometric reagents). 

• The synthesis of a new compound 
that is less toxic but has the same 
desirable properties as an existing 
compound, (e.g. anewpesticidethat 
is toxic only to target organisms and 
bio-degrades to environmentally 
benign substances) 

Green chemistry / technology has 
been developed in almost all branches 
of chemistry including organic, bio- 
chemistry, inorganic, polymer, toxicology, 
environmental, physical, industrial etc. 

The Principles of Green Chemistry 

• It is better to prevent waste 
generation than to treat or clean up 
waste after it is generated. 

• Wherever practicable, synthetic 
methodologies should be designed 
to use and generate substances that 
posses little or no toxicity to human 
health and the environment. 

• Chemical products should be 
designed to preserve efficacy of 
function while reducing toxicity. 




Fig. 7.9 Green chemistry 



List of some of the products 
produced by the process of green 
chemistry 

• Lead free solders and other product 
alternatives to lead additives in paints 
and the development of cleaner 
batteries. 

• Bio-plastics: Plastics made from 
plants including corn, potatoes or 
other agricultural products. 

• Flame resistant materials. 

• Halogen free flame retardants. 
e.g. silicon based materials can be used. 
Future products 

• A raw material feedstock should 
be renewable rather than depleting 
whenever technically and 
economically practical. 

• Catalytic reagents are superior to 
stoichiometric reagents. 

• Green Chemistry is applicable to 
all aspects of the product life cycle 
as well. Finally, the definition of 
green chemistry includes The 
term "hazardous". It is important to 
note that green chemistry is a way 
of dealing with risk reduction and 
pollution prevention. 

PVC and Lead 

New lead free solders with lower heat 
requirements are being developed. 

Beware of Green washing 

Green chemistry is not a panacea. We 
must be vigilant in making sure that what 
is called "Green Chemistry really pushes 
towards a more sustainable world and not 
simply green washing". 



7.7. SCIENCE TODAY - 

TOWARDS A GLOBAL 
VILLAGE 

Global village 

Global village is the term used to mean 
that world had shrunk into a village by 
means of different media types, most 
especially the world wide web, making 
It is easy to pass across messages (like 
news) thereby making the world become 
a single village where people can easily 
contact each other quicker. 



What is global village? 

A term that compares the world to a 
small village, where fast and modern 
communication allows news to reach 
quickly. The use of electronics for faster 
communication is a global village concept. 

What is the global electronic village? 

Global electronic village (GEV) is a term 
used to refer to a village without borders; 
it refers to connecting people around the 
world technologically through Information 
Communication Technologies (ICTS). 




Fig. 7.10 Global village 



Global Village (GV) is located at a 
distance of 12 kms from Bangalore on 
the Bangalore - Mysore Expressway 
and easily accessible by road. Spread 
over 110 acres of greenery, the project 
will house a cluster of technology 
companies in a campus type setting. 
The Buildings nestle among the lush 
green of manicured lawns, coconut 
palms and an eclectic mix of old trees 
in a serene and dust free environment. 
The Technology Campus has been 
conceptualized and designed 



by a team of reputed Indian and 
international architects and landscape 
designers.Ample residential facilities 
are in close proximity to the campus. 
The estimated driving time to GV 
from the heart of Bangalore city is 
approximately 20 minutes. 

Kshema Technologies have the 
distinction of being the first of GTV's 
companies to move into the campus with 
an 80,000 sq ft facility to house 600 
employees. 



CONSERVATION OF ENVIRONMENT 




The term global village was coined by Marshall McLuhan. He emphasized that "this 
forces us to become more involved with one another from countries around the world 
and be more aware of our global responsibilities". Similarly, web-connected computers 
enable people to link their web sites together. This new reality has implications for 
forming new sociological structures within the context of culture. 



EVALUATION 



PART A 

Multiple choice questions 

1. Which of the following groups contain 
only bio degradable items? 

(Grass, flowers and leather ; Grass, 
wood and plastic ; Fruit peels, cake 
and plastic ; Cake, wood and grass) 

2. Which of the following constitute a 
food chain? 

(Grass, wheat and mango ; Grass, 
goat and human ; Goat, cow and 
elephant ; Grass, fish and goat) 

3. Which of the following are 
environmental friendly practices? 

(carrying cloth bags to carry the 
purchase items during shopping, 
switching off light and fans when not 
in use, use the public transport, all 
the above) 

4. what is called as 'black gold'? 

(hydrocarbons, coal, petroleum, 
ether) 

5. odd one out. 

(Plants, grasshopper, frog, tiger, snake) 

6. Example for product of green 
chemistry is 

(plastic, paper, bio plastics, halogen 
flame retardants) 



7. green house gas which causes 

climate change and global warming. 

(hydrogen, oxygen, nitrogen, carbondioxide) 

8. The forms decomposer in the 

pond ecosystem (plants, bacteria, 
frog, phytoplanktons) 

9. chemical is used in 

seeding clouds (potassium iodide, 
calcium carbonate, sulphurdioxide, 
ammonium phosphate) 

10. Example for fossil fuel is 
(copper, iron, magnesium, coal) 

PART B 

11. Study the food chain below, correct it and 
convert into a pyramid of energy. 

Mulberry -> Sparrow -> Caterpillar -> Kite 

12. Study the illustration and answer the 
question. 

a. which line (A or B) represent the 
flow of energy? Why do you say so? 

b. Give an example of a decomposer. 

13. Study the food chain. 

Paddy -> Mouse -> Snake -> Kite 

If the producer has a STORED UP 
ENERGY OF 500 k GAL. How much 
of it goes to the organism at the third 
trophic level get from it? 



-• 




1 Producers 


]<:..B 


/" 


*> , 


1 Producers 


iHerbivoresI 


f 


u 


1 Soil, Air 1 


jcarnivores 1 


V 


^/ 


[Decomposers 


]v- 



14. 

a. Name the processes noted as no. 
land 3 

b. Define the process 1 

c. Name any one fossil fuel. (**) 

PARTC 

15. a) Classify the following substances - 

wood, paper, plastic and grasses. 

b) Give detailed account on your 
classification. 

16. In your area there is scarcity of water 
due to this the people are affected. 

Atmosphere 



Decompo 
-sition 



Animals 




Fossil 
plants 




Green 
plants 



So what are the measures to be taken 
by you to meet out the scarcity of 
water. 
17. Smoke, smoke everywhere smoke. 
Do you agree this situation is good for 
health. List out the harmful effects 
of coal burning. 




Sholas and grasslands of 

western ghats are the sources of 

all our South Indian rivers. All the 

hillocks in the upper mountains 

have this unique ecosystem, which 

we cannot create. 



FURTHER REFERENCE 

Books: 1. Plant Ecology Sheela.R.S and Chandel .P.S 

2. New development in green chemistry V.K. Atlerwalia, M. Kidwai 
Website: www.enviroliteracy.org/article.php/600 html 





8. Waste water management 



Human beings have been abusing 
the water-bodies around the world by 
disposing into them all kinds of wastes. 
We tend to believe that water can wash 
away everything not taking cognizance 
of the fact that the water bodies are our 
life line as well as that of all other living 
organisms. 

Can you list out the things we tend to 
try and wash away through our rivers and 
drains? 

Due to such activities of human 
being, the ponds, lakes, streams, rivers, 
estuaries and oceans are becoming 
polluted in several parts of the world. So 
we should manage the waste water in 
order to prevent the water pollution and 
its effects on our life. 

8-1- JOURNEY OF WATER 

Water, a precious physical substance, 
is essential to all living organisms. All 
biological functions and cell metabolism 
require water. Because of this feature, 
without water, life cannot be expected on 
the earth. 



Water cycle 

Large quantity of water is present 
to an area of about 1400 million km^ in 
the entire globe. This water evaporates 
from moist surfaces, falls as rain or snow, 
passes through lake, rivers, entered into 
the ground water table and to the ocean, 
also fixed in glaciers and deposited over 
mountains. Plants absorb water from the 
soil, utilized for its metabolic activities 
and release it into the atmosphere 
mainly through transpiration and all living 
organisms utilize water. 

Sources of water 

Water is widely distributed in nature 
and occurs in number of forms viz., 
solid, liquid and vapour. Rainfall brings 
the available primary source of water 
over the earth surface. Ocean water 
is the largest among all the water 
resources. A little quantity of water i.e., 
2.4 percent, water is fresh and most 
of this water is in glaciers or in ground 
water. Geologic layers containing water 
is known as aquifers of underground 
water. On some areas of the earth's 



crust, fresh water flows freely which 
is called as an artesian well or spring. 
Rivers carry huge volume of water for 
discharge into the lakes and ponds. 
Wetlands, swamps and marshes play a 
vital role in this journey of water. 

8.2. SEWAGE 

Sewage is formed from residential, 
institutional, commercial and industrial 
establishments and includes household 
waste liquid from toilets, baths, showers, 
kitchens, sinks and so forth that is 
disposed of via sewers. 

8.3. TREATMENT 

Sewage can be treated close to where 
it is created (in septic tanks, biofilters or 
aerobic treatment systems), or collected 
and transported via a network of pipes 
and pump stations to a municipal 
treatment plant (see sewage and pipes 
and infrastructure). Sewage collection and 
treatment is typically subject to local, state 
and central regulations and standards. 
Industrial sources of waste water often 
require specialized treatment process. 

Conventional sewage treatment may 
involve three stages called primary, 
secondary and tertiary treatment. 



PRETREATMENT 




TERTIARY 



Fig. 8.1 Sewage water treatment 



Primary treatment 

Primary treatment consists of 
temporarily holding the sewage in a 
quiescent basin where heavy solids can 
settle to the bottom while oil, grease 
and lighter solids float over the surface. 
The settled and floating materials are 
removed and remaining liquid may be 
discharged or subjected to secondary 
treatment. 

Secondary treatment 

Secondary treatment is used to remove 
dissolved and suspended biological 
matter. Secondary treatment is typically 
performed by indigenous, water - borne 
micro organisms in a managed habitat. 
Secondary treatment may require a 
separation process to remove the micro 
organisms from the treated water prior to 
discharge or tertiary treatment. 

Tertiary treatment 

Tertiary treatment is defined as either 
chemical or treatment of Alteration done 
after primary and secondary treatment. 
Treated water is sometimes disinfected 
chemically or physically (for example 
by lagoons and micro filtration.). Before 
discharging into a stream, river, bay, 
lagoon or wetland, or it can be used for 
the irrigation of a golf course, green way 
or park. If it is sufficiently clean, it can 
also be used for groundwater recharge or 
agricultural purposes. 

Bioremediation in sewage treatment 

Bioremediation can be defined 
as any process that is done by the 
use of microorganisms, fungi or their 
enzymes to treat the contaminants. 
Nitrosomonas europaea can be used 



LIFE PROCESSES 




ACTIVITY 8.1 



• Find out how the sewage in your locality is treated. Are there mechanisms to 
ensure that local water bodies are not polluted by untreated sewage. 

• Find out how the local industries in your locality treat their wastes. Are there 
mechanisms in place to ensure that the soil and water are not polluted by the 
waste? 



to treat sewage, freshwater, walls 
of buildings and on the surface of 
monuments especially in polluted areas 
where there is high levels of nitrogen 
compounds. 

8.4. DOMESTIC PRACTICES: 

Sewage is created by residential house 
hold waste liquid from toilets, bathroom, 
showers, kitchens, and so forth then is 
dispersed of via sewers. 

The seperation of draining of 
household waste into grey water and 
black water is becoming more common 
in the developed world, with grey water 
being permited to be used for watering 
plants or recyling for flushing toilets. 

Waste water 

Waste water is often reffered to as grey 
water. Any water that has been used in 
the home, with the exception of water 
in the toilet can be reffered to as waste 
water. 

This water could be reused for a 
multitude of purposes, including, 

1. watering yard and gardens, 

2. Filtering septic systems, 

3. Irrigating fields, 



Benefits of house hold waste water 
recycling systems, 

1. Less fresh water usage, 

2. Reduce strain in septic tanks, 

3. Recharge ground water, 
4. Encourage plant growth. 

8.5. SANITATION AND 
DISEASES : 

Water supply, sanitation and health 
are closely interrelated. Poor hygiene, 
inadequate quantities and quality of 
drinking water and lack of sanitation 
facilities cause millions of the world's 
poorest people to die from preventable 
diseases each year. Water contaminated 
by human, chemical or industrial wastes 
can cause a variety of communicable 
diseases through ingestion or physical 
contact. 

Water-borne diseases 

Water -borne diseases are caused 
by the ingestion of water communicated 
by human or animal faeces or urine 
containing pathogenic bacteria or viruses; 
include cholera, typhoid, amoebic and 
bacillary dysentery and other diarrhoeal 
diseases. 

Water-washed diseases are caused by 
poor personal hygiene and skin or eye 



ACTIVITY 8.2 



• Practice regularly to wash your hands thoroughly before and after using the 
toilets. 

• Food and water containers should be cleaned and has to be closed when they 
are in use. 

• During flood and other natural calamities, water should be used only after 
boiling. 

• People live near hazardous industrial waste accumulating or water pollution 
areas should be very careful in using the ground water. 



contact with contaminated water; include 
scabies, trachoma and flea, lice and tick- 
borne diseases. 

Water-based diseases are caused by 
parasitesfound in intermediate organisms 
living in water; include dracunculiasis, 
schistosomiasis and other helminthes. 

Water-related diseases are caused 
by insect vectors which breed in water; 
include dengue, filariasis, malaria, 
onchocerciasis, trypanosomiasis and 
yellow fever. 

• Contaminated water that is 
consumed may result in water- 
borne diseases including viral 
hepatitis, typhoid, cholera, 
dysentery and other diseases that 
cause diarrhoea. 

• Without adequate quantities of 
water for personal hygiene, skin 
and eye infections spread easily. 

• Water- based diseases and water- 
related vector-borne diseases can 
result from water supply projects. 
They inadvertently provide habitats 
for mosquitoes and snails. They are 



intermediate hosts for parasites that 
cause malaria. Schistosomiasis, 
lymphatic filariasis and Japanese 
encephalitis. 

Drinking water supplies that contain 
high amounts of certain chemicals 
(like arsenic and nitrates) can cause 
serious diseases. 

Inadequate water, sanitation and 
hygiene, account for a large part of 
the burden of illness and death in 
developing countries. 

Lack of clean water and sanitation 
is the second most important risk 
factor in terms of the global burden 
of diseases, after malnutrition. 

Approximately 4 billion cases of 
diarrhoea per year cause 1.5 million 
deaths, mostly among children under 
five. 

Intestinal worms infect about 10 
percent of the population of the 
developing world, and can lead to 
malnutrition, anaemia and retarded 
growth. 

300 million people suffer from 
malaria. 



LIFE PROCESSES 




8-6- ALTERNATIVE 

ARRANGEMENT FOR 
SEWAGE DISPOSAL 

Wherever crops are grown, they 
always need nutrients and water. 
Wastewater is often used in agriculture 
as it contains water, minerals, nutrients 
and its disposal is often expensive. 
Where effluent is used for irrigation, good 
qualitywatercan be reserved exclusively 
for drinking water. Wastewater can also 
be used as a fertilizer, thus minimizing 
the need for chemical fertilizers. This 
reduces costs, energy, expenditure and 
industrial pollution. Waste water is also 
commonly used in aquaculture or fish 
farming. 

8.7- SANITATION IN PUBLIC 
PLACES 

Wherever population density is high 
such as bus station or school, especially 
when they are eating food from the same 
source, there is a greater risk of the spread 
of diseases such as, cholera, hepatitis A,- 
typhoid and other diarrhoeal diseases. 

These places vary in the number of 
people using them, the amount of time 
that people spend there and the type of 
activity that occurs in the area, but all 
public places need to have adequate 
sanitation and hygiene facilities. 

Basic rules for sanitation in 
public places 

1. There should be sufficient toilet 
facilities. 



2. The toilet facilities should be 
arranged in separate blocks for 
men and women. 

3. The men's toilet blockshould have 
urinals and toilet compartments, 
the women's block have toilet 
compartments only. 

4. There must be a hand washing 
basin with clean water. 

5. There must be a clean and reliable 
water supply for hand washing, 
personal hygiene and flushing of 
the toilet facilities. 

8-8- ENERGY MANAGEMENT 

What is Energy Management? 

"Energy management" is a term 
that has a number of meanings, but 
we are mainly concerned with the 
one that relates to saving energy in 
business, public-sector / government 
organizations and homes. 

Energy saving measures 

Energy management is the process of 
monitoring controlling and conserving energy 
in a living home or in any organization. 

8.8.1. Energy Audit 

An energy audit is an inspection, survey 
and analysis on energy flows for energy 
conservation in a building, process or 
system. It is done to reduce the amount 
of energy input into the system without 
negatively affecting the output(s). 

Home energy audit 

A home energy audit is a service 
where the energy efficiency of a house is 
evaluated by a person using professional 



equipment (such as blower doors and 
infra-red cameras), with the aim to 
suggest the best ways to improve energy 
efficiency in heating and cooling the 
house. 

An energy auditofahome may involve 
recording various characteristics of the 
building envelope including the walls, 
ceilings, floors, doors, windows and 
skylights. The goal of this exercise is to 
quantify the building's overall thermal 
performance. The audit may also 
assess the efficiency, physical condition 
at programming of mechanical systems 
such as the heating, ventilation, air 
conditioning equipment and thermostat. 

A home energy audit may include a 
written report estimating energy use given 
local climate criteria, thermostat settings, 
roof overhang, and solar orientation. This 
could show energy use for a given time 
period, say a year, and the impact of any 
suggested improvements per year. The 
accuracy of energy estimates are greatly 
improved when the homeowner's billing 
history is available showing the quantities 
of electricity, natural gas, fuel oil, or other 
energy sources consumed over a one or 
two-year period. 

A home energy audit is often used to 
identify cost effective ways to improve the 
comfort and efficiency of buildings. In 
addition, homes may qualify for energy 
efficiency grants from central government. 

Energy audit in schools 

The function of an energy audit is to 
expose different ways to affect energy 



ACTIVITY 8.3 



Using a thermometer, observe 
the room temperature of 
your class room and the 
temperature under a Neem 
tree on an hot day. 

Burn the tungsten lamp and 
compressed fluorescent 

lamps and compare the 
energy consumption. 



consumption and identify numerous options 
for reducing energy consumption. 

The money your school saves will 
be available to fund important school 
projects, but just as important, energy 
savings help the Earth by reducing 
resource use and environmental 
pollution. By improving efficiency in 
places like our schools, we can get 
the same benefits while using less 
energy. For example, substituting 
energy efficient, compact fluorescent 
light bulbs (CFL) for standard 
incandescent bulbs will save on 
average up to 6,000 megawatts of 
electricity each year. 

There are many ways you can help 
your school save money on water usage, 
such as checking for leaks in the system, 
reducing water usage (especially hot 
water), and improving the efficiency of 
water delivery. 

Another important way to save energy 
at your school is through recycling. This 
can be done all over the school. For 
example, you can save by recycling 
paper milk cartons from the lunch room 
or printer cartridges in the copy room. By 
recycling paper, milk cartons and other 



LIFE PROCESSES 



U 



materials, schools are able to reduce 
the amount of waste they produce. This 
can garner significant savings as well as 
benefit the environment. 

8.8-2. Renewable sources 

A natural resource is a renewable 
resource, if it is replaced by natural 
processes at a rate comparable or faster 
than its rate of consumption by humans. 
Solar radiation. Hydrogen, Wind and 
hydroelectricity are in no danger of a lack 
of long term availability. 

Solar Energy 

Solar energy is the energy derived 
directly from the sun. Along with nuclear 
energy, it is the most abundant source of 
energy on earth. The fastest growing type of 
alternative energy increasing at 50 percent 
a year ,is the photovoltaic cell, which 
converts sunlight directly into electricity. The 
sun yearly delivers more than 10000 times 
the energy that humans currently use. 



Hp-^ .>A Solar incidence 




Module 







Battery changer 
controller 



?= 



p 



Battery 



^ 



uj 



Battery system 



=^ 



DC loads 



Fig. 8.2 Solar Energy 

Hydrogen 

The hydrogen has been found to be 
a good choice among all the alternative 
fuel options . It can be produced in 
virtually unlimited quantities with on 



ACTIVITY 8.4 



Study the structure and working of 
a solar cooker and / or a solar water 
heater, particularly with regard to 
how it is insulated and maximum 
heat absorption is ensured. 
Design and build a solar cooker 
or water heater using low cost 
material available and check what 
temperatures are achieved in your 
system. 

Discuss what would be the 
advantages and limitations of using 
solar cooker or water heater. 



hand production technologies. It has 
been established that hydrogen can 
meet all the energy needs of human 
society, including power generation more 
efficiently and more economically than 
petro fuels, and with total compatibility with 
the environment. In addition, hydrogen 
is non-toxic reasonably safe to handle, 
distribute and use as a fuel. Hydrogen 
has the highest mass energy content - 
its heat of combustion per unit weight is 
about 2.5 times that of hydro carbon fuel, 
4.5 times that of ethanol and 6.0 times 
that of methanol. Its thermodynamic 
energy conversion efficiency of 30-35 % 
is greater than that of gasoline (20-25%). 

Wind Power 

Wind power is derived from uneven 
heating of the Earth's surface from the sun 
and the warm core. Most modern wind 
power is generated in the form of electricity 
by converting the rotation of turbine 
blades into electrical current by means 
of an electrical generator. In wind mills 
(a much older technology) wind energy 



MORE TO KNOW 



Denmark is called the country of "winds". More than 25% of their electricity 
needs are generated through a vast network of windmills. In terms of total output, 
Germany is the leader, while India is ranked 5*^ in harnessing wind energy for 
the production of electricity. It is estimated that nearly 45000MW of electrical 
power can be generated if India's wind potential is fully exploited. The largest 
wind energy farm has been established near Kanyakumari in Tamilnadu and it 
generates 380MW of electricity. 



is used to turn mechanical machinery to 
do physical work, like crushing grain or 
pumping water. 



Fossil Fuels 

Fossil fuels are energy rich, combustible 
forms of carbon or compounds of carbon 
formed by the decomposition of biomass 
buried under the earth over million of years. 




Fig. 8.3 Windmills 

8.8-3- Non-renewable sources 

A non-renewable resource is a natural 
resource which cannot be produced, 
grown, generated or used on a scale 
which can sustain its consumption 
rate. These resources often exist in a 
fixed amount, or are consumed much 
faster than nature can create them. 
Fossil fuels (such as coal, petroleum 
and natural gas) and nuclear power 
(uranium) are example. 



Fig. 8.4 Coalmining 

Fossil Fuel - Coal 

It is a black mineral of plant origin which is 
chemically, a complex mixture of elemental 
carbon, compounds of carbon containing 
hydrogen, oxygen, nitrogen and sulphur. 

Petroleum 

Petroleum is a dark, viscous, foul 
smelling liquid, a mixture of solid, liquid 
and gaseous hydro carbons with traces of 
salt, rock particles and water. 



LIFE PROCESSES 



U 



ACTIVITY 8.5 



Debate the following two issues in 
class. 

The estimated coal reserves are 
said to be enough to last us for 
another 200 years. Do you think 
we need to worry about coal 
getting depleted in this case? Why 
or why not? 

It is estimated that the sun will last 
for another 5 billion years. Do we 
have to worry about solar energy 
getting exhausted? Why or why 
not? 

On the basis of the debate, 
decide which energy sources 
can be considered i) exhaustible 
ii) inexhaustible iii) renewable iv) 
non-renewable. Give your reasons 
for each choice. 



Natural Gas 

The composition of natural gas is chiefly 
methane (> 90%) with traces of ethane 
and propane. It is found associated with 
other fossil fuels, in coal beds, as methane 
clathrates and it is created by methanogenic 
organisms in marshes, bogs, and land 
fills. It is an important fuel source, a major 
feedstock for fertilizers and a potent green 
house gas. 

Before natural gas can be used as a 
fuel, it must undergo extensive processing 
to remove almost all materials other than 
methane. These by-products of that 
processing include ethane, propane, 
butane, pentane and higher molecular 
weight hydrocarbons, elemental sulphur, 
carbon-di-oxide, water vapour and 
sometimes helium and nitrogen. 



Natural gas is often informally referred to 
as simply gas, especially when compared to 
other energy sources such as oil or coal. 

USES 

Power Generation: Natural Gas is a major 
source of electricity generation through the 
use of gas turbines and steam turbines. 
Most grid peaking power plants and some 
off - grid engine - generators use natural 
gas. 

Domestic use: Natural gas is supplied to 
homes where it is used for such purposes 
as cooking in natural gas - power rangers 
and oven, natural gas heater clothes 
dryers, heating or cooling and central 
heating. Home or other building heating 
may include boilers, furnaces and water 
heaters. 

Natural gas is a major feedstock for the 
production of ammonia, for use in fertilizer 
production. 

Other: Natural gas is also used in the 
manufacture of fabrics, glass, steel, plastics, 
paint and other products. With man's ever 
increasing need for energy , he has been 
using fossil fuels indiscriminately. In the 
process, harmful materials contributing to 
air pollution are being produced. 

8.8A Bio-fuels - Generation and use 

Biofuels are a wide range of fuels 
which are in some way derived from 
biomass. The term covers solid biomass, 
liquid fuels and various biogases. Bio 
fuels are gaining increased public and 
scientific attention driven by factors such 
as oil price hikes, the need for increased 
energy security and concern over green 
house gas emissions from fossil fuels. 



The various liquid bio fuels for 
transportation are 

1. Bio alcohol 

2. Green diesel 

3. Bio diesel 

4. Vegetable oil 

5. Bio ethers 

6. Bio gas 

Bioalcohol (Bioethanol) 

Bioethanol is an alcohol made by 
fermenting the sugar components of 
plant materials and it is made mostly from 
sugar and starch crops. With advanced 
technology being developed, cellulosic 
biomass, such as trees and grasses are 
also used as feed stocks for ethanol 
production. Ethanol can be used as a fuel 
for vehicles in its pure form. Bioethanol is 
widely used in the USA and Brazil. 

Biodiesel: Biodiesel is made from 
vegetable oil and animal fats. It is used 
as a fuel for vehicles in its pure form. 

Biogas: Biogas is produced by the 
process of anaerobic digestion of 
organic material by anaerobes. It can 
be produced either from bio degradable 
waste material or by the use of energy 
crops fed into anaerobic digesters to 
supplement gas yields. The solid by 
product, digestable can be used as 
biofuel or fertilizer. 

8.8.5 ENERGY 

CONSERVATION & HOW 
WE CAN HELP 

Energy conservation 

Energy conservation refers to efforts 
made to reduce energy consumption 



in order to preserve resources for 
the future and reduce environmental 
pollution. It can be achieved through 
efficient energy use or by reduced 
consumption of energy services. Energy 
conservation may result in increase of 
financial capital, environmental value, 
national security, personal security 
and human comfort. Individuals and 
organizations that are direct consumers 
of energy may want to conserve energy 
in order to reduce energy costs and 
promote economic security. Industrial 
and commercial users may want to 
increase efficiency and thus maximize 
profit. Electrical energy conservations 
are the important element of energy 
policy. 



Lighting 



1. Turn off the lights when not in use. 

2. De-dust lighting fixtures to maintain 
illumination. 

3. Focus the light where you need. 

4. Use fluorescent bulbs. 

5. Use electronic chokes in place of 
conventional copper chokes. 



Fans 



1. Replace conventional regulators with 
electronic regulators for ceiling fans. 

2. Install exhaust fans at a higher 
elevation than ceiling fans. 



Electric Iron 



1. Select iron boxes with automatic 
temperature cut off. 

2. Use appropriate regulator position 
for ironing. 



LIFE PROCESSES 



U 



3. Do not put more water on clothes 
while ironing. 

4. Do not iron wet clothes. 



Gas Stove 



When cooking on a gas burner, use 

moderate flame settings to conserve 

LPG. 

Remember that a blue flame 

means your gas stove is operating 

efficiently. 

If there is yellowish flame, this 

indicates that the burner needs 

cleaning. 

Use pressure cooker as much as 

possible. 

Use lids to cover the pans while 

cooking. 

Use solar water heater - a good 

replacement for a electric water 

heater. 



Electronic Devices 



Do not switch on the power when TV 
and Audio systems are not in use. 
i.e., idle operation leads to an energy 
loss of 10 watts / device. 
Battery chargers such as those 
for laptops, cell phones and digital 
cameras, draw power whenever 
they are plugged in and are very 
inefficient. Pull the plug and save. 



Washing Machine 



1. Always wash only with full loads. 

2. Use optimal quantity of water. 

3. Use timer facility to save energy. 

4. Use the correct amount of detergent. 

5. Use hot water only for very dirty 
clothes. 

6. Always use cold water in the rinse 
cycle. 



EVALUATION 



PART A 

1. Example for water-borne disease is 

(scabies, dracunculiasis, trachoma, 
typhoid) 

2. The settled and floating materials are 

removed by this treatment method. 



(primary treatment, 
treatment, tertiary 
peripheral treatment) 



secondary 
treatment. 



3. Which is a non-renewable resource? 

(coal, petroleum, natural gas, all 
the above) 



is the chief component of 



natural gas. 

(ethane, 
butane) 



methane, propane. 



PARTE 

5. The bar graph indicates the presence 
of the infectious diseases in two cities 
A and B. Observe it and answer the 
questions given below. 

1. Dengue fever 2. Rat fever 
3. Cholera 4. Chikungunya 

a. What may be the reason for the 
disease in the city A? 



0) 



o 

o 

o 

> 
















A B 


* 






1 


3 


► 


i 


% 





b. Which city needs more careful 
waste disposal and cleaning? 

c. How can the disease be controlled 

in city A? 

The pie diagram represents a survey 
result of infectious diseases of a 
village during 2008 - 2009. Analyse it 
and answer the following chart 




Which diseases affect the majority of 
the population? 



a. How are these diseases 
transmitted? 

b. Write any three measures to 
control the other two diseases. 

7. Match the suitable renewable and non- 
renewable sources. 



Sources 


A 


B 


C 


Renewable 


Coal 


Wind 


Petroleum 


Non- 
Renewable 


Hydrogen 


Natural 
gas 


Solar 
energy 



8. Odd one out 

a. bio alcohol, green diesel, bio ethers, 
petroleum 

b. cholera, typhoid, scabies, dysentry 

9. A non renewable resource is a natural 

resource if it is replaced by natural 
process at a rate comparable or faster 
than its rate of consumption by humans. 
Read this statement and confirm 
whether it is correct or incorrect. If it is 
incorrect give correct statement. 

10. Pick out the suitable appliances to 
conserve the electric energy. 

Florescent bulbs, copper choke, solar 
water heater, electric water heater, 
tungsten bulbs, electronic choke. 



FURTHER REFERENCE 




Books: 1. Land treatment of waste water M.B. Gohil Publisher 


New Age 


International (p) Ltd. 




Website: 2. Sewage, en.wikipedia-org/wiki/sewage -treatment. 





Chapter 






SOLUTIONS 



9. Solutions 




Result of health drink 

Anu has got back home from playfield 
after winning a match. She is received 
by her mother cheerfully with a glass of 
health drink. 

Anu: Mother! What is this? 

Mother: This is your health drink - a 
solution of fruit juice and sugar 
for your revitalisation. 

Solutions are of great importance 
in everyday life. The process of food 
assimilation by man is in the form of 
solution. Blood and lymph are in the form 




Health drink 

of solution to decide the physiological 
activity of human beings. 

A solution is a homogeneous mixture 
of two (or) more substances. 

All solutions exist in homogeneous 
form. Homogeneous refers to the state 
in which two (or) more substances, that 
are uniformly present in a given mixture. 
If a solution contains two components, 
then it is called as a Binary Solution. 

Salt solution containing common salt 
in water is a suitable example for binary 
solution. 





Solute Solvent _ Solution 

(salt) (water) ~ (salt solution) 

Fig. 9.1 A solution is a homogenous mixture of solute and solvent 



SOLUTIONS 



U 



9-1- SOLUTE AND SOLVENT 

In a solution, the component present in 
lesser amount by weight is called solute 
and the component present in a larger 
amount by weight is called solvent. 
Generally a solvent is a dissolving 
medium. It surrounds the particles of 
solute to form solution. 

In short, a solution can be represented, 
as follows 

(Solute + Solvent -^ Solution) 

9-2, TYPES OF SOLUTIONS 

9.2.1. Based on the particle size 

Based on the particle size of the 
solute, the solutions are divided into 
three types. 

1. True solutions: It is a homogeneous 
mixture that contains small solute 
particles that are dissolved throughout 
the solvent eg. Sugar in water. 

2. Colloidal solutions: It is a 

heterogeneous mixture made up of two 




Sugar 



Water 



Sugar 
solution 




Fig. 9.2 Mixture of sugar and water 
forming true solution 



phases namely, dispersed phase and 
dispersion medium. The substance 
distributed as particles is called 
dispersed phase. The continuous 
phase in which the colloidal particles 
are dispersed is called dispersion 
medium. 

(Dispersed phase + Dispersion 
medium -^ Colloidal solution) 




Fat, vitamin, protein 

+ 




Water 




Milk 

Fig. 9.3 A mixture of milk powder and 

water forming colloid 



Suspensions: It is a heterogeneous 
mixture of small insoluble particles in a 
solvent. In a suspension, the particles 
of solid stay in clusters that are large 
enough to be seen (e.g. Chalk powder 
in water). 



38888888S 



-^ 




Chalk 



Water 



Suspension 



Fig. 9.4 A mixture of chalk and water forming 
suspension 



MORE TO KNOW 



Tyndall effect, The phenomenon 
by which colloidal particles scatter 
light is called Tyndall effect. If a 
beam of light is allowed to pass 
through a true solution, some 
of the light will be absorbed and 
some will be transmitted. The 
particles in true solution are not 
large enough to scatter the light. 
However if light is passed through 
a colloidal solution, the light is 
scattered by the larger colloidal 
particles and the beam becomes 
visible. This effect is called 
TYNDALL EFFECT 



ACTIVITY 9.1 



Students may be asked to observe 
the scattering of light (Tyndall effect) 
when sunlight passes through the 
window of the class rooms. The dust 
particles scatter the light making the 

path of the light visible. 




Fig. 9.5 Tyndall effect in nature 



MORE TO KNOW 



Brownian motion: The 

phenomenon by which the colloidal 
particles are in continuous random 
motion is called Brownian motion. 

Brownian motion is named in 
honour of ROBERT BROWN a 
biologist.He observed the motion 
of the particles in suspension of 
pollen grains in water. 




Fig. 9.6 Brownian motion 



SOLUTIONS 



U 



Comparing the properties of true solution,colloidal solution and suspension 



Property 


True Solution 


Colloidal Solution Suspension _ 


Particle size in A 
(1A= 10-i°m) 










• • ••• •• 




UP 


•^^^--^^F— i-^Tgr^ T>y- 


More than 1000 A 


m 




lAto10A 


10Ato1000A 


Appearance 


Transparent 


Translucent 


Opaque 


Visibility of 
particles 


Not visible even under 
ultra microscope 


Visible under ultra 
microscope 


\ Visible to the 
naked eye 


Nature 


Homogeneous 


Heterogeneous 


Heterogeneous 


Diffusion of 
particles 


diffuses rapidly 


diffuses slowly 


diffusion does not 
occur 


Scattering effect 


Does not scatter ligiit 


It scatters light 


It does not scatter 
light 



9.2.2, Based on the type of solvent. 

Based on the type of solvent solutions 
are classified into two types 

1. Aqueous solution: The solution 
in which water acts as a solvent, is 
called aqueous solution. For e.g., 
sugar solution. 

2. Non-aqueous solution: The solution 
in which any liquid other than water acts 
as a solvent is called non-aqueous 
solution. Solution of sulphur in 
carbon disulphide is a suitable 
example for non-aqueous solution. 
(Benzene, ether, CS^, are some of the 
examples for non aqueous solvents.) 

9.2.3. Based on the amount of 
solute in the given solution 

Based on the amount of solute in the 
given amount of solvent, solutions are 
classified into the following types. 



1. Unsaturated solution 

2. Saturated solution 

3. Supersaturated solution 

1. Unsaturated solution: A solution in 
which the solute is in lesser amount in 
comparison with the solvent is called 
unsaturated solution. In this, addition 
of solute is possible till the solution 
reaches the point of saturation. 

e.g., 5gor 10gor20gof NaCI in 100g 
water 

2. Saturated solution: A solution in 
which no more solute can be dissolved 
in a definite amount of solvent at a 
given temperature is called a saturated 
solution e.g., 

i) A saturated solution of CO in HO 



ii) 36g of NaCI in lOOg of water at room 
temperature forms saturated solution 

3. Super saturated solution: A solution 
which has more of solute at a given 
temperature than that of saturated 
solution is called super saturated 
solution. 



MORE TO KNOW 



Nitrogen in earth soil is an example 
for saturated solution in nature. 
(Earth soil cannot store more N^ 
than it can hold) 



ACTIVITY 9.2 



Test whether a solution is saturated, 
unsaturated or super-saturated with 
respect to the addition of salt at a 
particular temperature to the solution. 

Take a beaker containing 100ml of 
water, three packets of common salts 
each weighing 20g, 16g, and 1g and a 
glass stirrer (see fig 9.7). 

Record your observations after the 
addition of each packet in the given 
order followed by stirring at each 
stage. 




Unsaturated 



Saturated 



Super 
Saturated 



Fig. 9. 7 To test Saturation, Unsaturation and 
Super Saturation in a given solution 



9.2.4 Based on the physical state of the solute and the solvent the solutions are of 9 
types. 



Solute 


Solvent 


Examples 


Solid 


Solid 


Alloys 


Solid 


Liquid 


Sugar solution 


Solid 


Gas 


Smoke 


Liquid 


Solid 


Cheese 


Liquid 


Liquid 


Milk 


Liquid 


Gas 


Cloud 


Gas 


Solid 


Cork 


Gas 


Liquid 


Soda water 


Gas 


Gas 


Helium-oxygen mixture (for deep sea diving ) 



SOLUTIONS 



U 



9-3- SOLUBILITY 

Solubility of a solute in a given solvent 
at a particular temperature is defined as 
the number of grams of solute necessary 
to saturate lOOg of the solvent at that 
temperature. For example 

Solubility of CuSO^ in H^O is 20.7g 
at 20°C 



ACTIVITY 9.3 



Determine the solubility of a solid (say 
KCI) in water at room temperature. 

• Prepare saturated solution of KCI 
in about 30 ml of water at room 
temperature. Add more of KCI 
ensuring that solution is saturated 
and some KCI is left undissolved. 

• Filter the solution to remove solid KCI. 

• Find temperature of the solution by 
dipping a thermometer in it. 

• Evaporate the solution to dryness by 
using a low flame to avoid bumping. 

• Allow the dish and solid to cool to room 
temperature. Place the dish and solid 
in a dessicator containing anhydrous 
calcium chloride (calcium chloride is 
dehydrating agent, it absorbs moisture). 



SATURATED 

SOLUTION 

OF KCI 




SATURATED SOLUTION 

OF KCI SAND BATH 




MORE TO KNOW 



Dilute and concentrated solutions: 

Concentration of a solution is the 
amount of solute dissolved in a 
given amount of solvent. A solution 
containing less amount of solute 
is known as dilute solution whereas a 
solution containing large amount 
of solute is known as concentrated 
solution. It may be noted that dilute 
and concentrated are the relative 
terms and they have only quantitative 
meaning. 



Take out the evaporating dish and 
again weigh it. 

The observation and calculation are 
given as follows. 



Weight of the dish 


= Wg 


Weight of dish + saturated 
solution of KCI 


= W,g 


Weight of dish + dry KCI 


= W,g 



Calculation 

Weight of saturated solution = (W^ - W)g 

Weight of KCI = (W^ - W)g 

Weight of water present 
in saturated solution 

= [(W, - W) - (W, - W)]g 

= [(W, - W,)g 
Weight of KCI 



Solubility of KCI = 



Weight of solvent 

(W^ - W) 



xlOO 



Fig. 9.8 Determination of solubility 



(W, - W,) 



xlOO 




Solubility of some ionic compounds at 25°c 



Substance 


Solubility 
(g per lOOg 
water) 


NaCI 


36g 


NaBr 


95g 


Nal 


184g 


NaNOg 


92g 



9.4. FACTORS AFFECTING 
SOLUBILITY 

1. Temperature 

2. Nature of solute (or) solvent 

3. Pressure 

1. Effect of temperature 

In endothermic process, solubility increases 
with increase in temperature. 

E.g., Solubility of KNO3 increases with 
the increase in temperature. 

In exothermic process, solubility 
decreases with increase in temperature. 

E.g., Solubility of CaO decreases with 
increase in temperature. 

2. Nature of solute and solvent 

Solubility of a solute in a solvent de- 
pends on the nature of both solute and 
solvent. A polar compound dissolves in a 
polar solvent. 



E.g., Common salt dissolves in water. 
A polar compound is less soluble (or) 
insoluble in a non polar solvent. 

3- Effect of pressure 

Effect of pressure is observed only in the 
case of gases. An increase in pressure 
increases the solubility of a gas in a liquid. 
For eg. CO^ gas is filled in soft drinks 
using the effect of pressure. 




Fig. 9.9 CO^ filled in soft drinks 



MORE TO KNOW 



Increase in pressure increases 
the solubility of gases. At a 
given temperature, the mass of 
gas dissolved in a fixed volume 
of liquid is directly proportional 
to the pressure of the gas on 
the surface of the liquid. This is 
called Henry's Law. 



SOLUTIONS 



U 



PROBLEM 1 

Take 10g of common salt and dissolve 
it in 40g of water. Find the concentration 
of solution in terms of weight percent. 

Weight percent 

Weight of the solute 
= X 100 

Weight of solute + Weight of solvent 

= -who ^ 10° = 200/0 



PROBLEM 3 

50g of saturated solution of NaCI at 
30°C is evaporated to dryness when 
13.2g of dry NaCI was obtained. Find the 
solubility of NaCI at 30°C in water. 

Mass of water in solution = 50-13.2 = 36. 8g 

Solubility of NaCI = 

Mass of NaCI 13.2 
X 100 = X 100 = 36g 

Mass of water 36.8 

Solubility of NaCI = 36g (appx.) 



PROBLEM 2 

2g of potassium sulphate was 
dissolved in 12.5 ml of water. On 
cooling, the first crystals appeared 
at 60X. What is the solubility of 
potassium sulphate in water at 60X? 

SOLUTION 

12.5 ml of water weighs 12. 5g. 

In 12. 5g of water, amount of potassium 
sulphate dissolved, is 2g 

In Ig of water, amount of potassium 
sulphate dissolved, is 2/12.5 g 

Hence in lOOg of water, amount 
of potassium sulphate dissolved, is 
(2x100)/12.5=16g. 

The solubility of potassium sulphate in 
water at 60°C is 16g. 



PROBLEM 4 

An empty evaporating dish weighs 

20. Og On the addition of saturated 
solution of NaNOg, the dish weighs 66. Og. 
When evaporated to dryness, the dish with 
crystals weighs 41. 5g. Find the solubility 
of NaN03 at 20°C. 

SOLUTION 

Weight of saturated solution of NaNOg 
= (66.0- 20.0) g = 46.0g 

Weight of crystals of NaNOg = (41.5-20.0) g 

= 21.5g 

Weight of water in saturated solution 
= (46.0-21.5) g = 24.5g 
Solubility of NaNOg = 

Weight of NaNOg Crystals , 



Weight of water 
21.5 



XlOO 



X 100 = 87. 7g 



24.5 



Solubility of NaNOg at 20°C is = 87. 7g in 
lOOg H^O 



EVALUATION 



PART - A 

1. A true solution is a homogenous 
mixture of solute and solvent. Chalk 
powder in water is a heterogenous 
mixture. Is it a true solution? 

2. Solution that contains water as the 
solvent is called aqueous solution. 
If carbon disulphide is a solvent in 
a given solution, then the solution is 
called . 

3. Solubility of common salt in lOOg water 
is 36g. If 20g of salt is dissolved in it 
how much more is required to attain 
saturation. 

4. If two liquids are mutually soluble, they 

are called liquids, (miscible, 

immiscible) 

5. When sunlight passes through 
window of the classrooms its path is 

visible. This is due to of light. 

(reflection, scattering) 

6. The particles in various forms are 
visible only under ultramicroscope. A 
solution containing such particles is 

called . (True solution/ 

colloidal solution) 

7. The mixture of gases used by deep 

sea divers is (Helium-oxygen, 

oxygen-nitrogen) 

8. Earth soil cannot store more nitrogen 
than it can hold. Hence earth soil is 



referred to be in a state of . 

(saturation, unsaturation) 

9. In an endothermic process, solubility 

increases with in 

temperature, (increase, decrease) 

PART - B 

10. From the table given below , furnish 
your points of inferences. 



Substance 


Solubility at 25°C 


NaCI 


36g 


NaBr 


95g 


Nal 


184g 



11 . Distinguish between the saturated and 
unsaturated solution using the data 
given below at a temperature of 25°C 

A. 16g NaCI in lOOg water 

B. 36g NaCI in lOOg water 

12. You have prepared a saturated 
solution of sugar. Is it possible to 
dissolve some more grams of sugar 
to this solution? Justify your stand. 

13. Find the concentration of solution in 
terms of weight percent if 20 gram of 
common salt is dissolved in 50 gram 
of water. 



FURTHER REFERENCE : 

BOOKS: 1 . Physical Chemistry: Puri & Sharma - Vishal Publication 

2. Advanced Chemistry: Bahl & Arun Bahl - S.Chand publishers 

WEBSITE: www.chemistry explained.com www.sparknotes.com 




ATOMS AND MOLECULES 




Rani shows a piece of chalk to Vani & 
asks her to break it into minute particles. The 
breaking spree, goes on and on endlessly and 
finally they come to conclude that the minute 
particle is a group of invisible atoms. They get 
set to probe further. 




EXPLORING THE ATOM 

The word atom is derived from the 
Greek word "Atomos" which means 
indivisible. John Dalton modeled atoms 
as hard indivisible spheres. 

His theory remained undisputed for 
about a century without any changes. 
However towards the end of 19th and 
in the beginning of 20th centuries, the 
introduction of matter wave concept by 
de Broglie, the principle of uncertainty 
by Heisenberg etc., paved the way for 
modern atomic theory or modified 
atomic theory. 




Fig. 10.1 Inner View of an atom 




10-1- MODERN ATOMIC THEORY 

The findings of modern atomic theory 

are given as follows. 

► Atom is considered to be a divisible 
particle. 

► Atoms of the same element may not 
be similar in all respects. 

eg: Isotopes (C/^^,C/^g 

► Atoms of different elements may be 
similar in some respects 



eg. Isobars (/Ar^^, 



Cat'.) 



20^ 



► Atom is the smallest particle which 
takes part in chemical reactions. 

► The ratio of atoms in a molecule may 
be fixed and integral but may not be 
simple 

e.g., C^2'^22^ii '^ ^^^ ^ simple ratio 
(Sucrose) 



ALBERT EINSTEIN 




When a nuclear reaction occurs the 
mass of the product is found to be 
less than the starting mass. The 

difference in mass is converted into 
energy in accordance with the equa - 
tion E = mc,^ where E = energy 
liberated, m = disappeared mass and 
c = speed of light. This famous equa- 
tion of Einstein, made revolution in 
nuclear science. 



► Atoms of one element can be 
changed into atoms of other element 
by transmutation. 

► The mass of an atom can be 
converted into energy. This is in 
accordance with Einstein's equation 
E = mc^ 

10-2, AVOGADRO'S HYPOTHESIS 

Amedeo Avogadro put forward 
hypothesis and is based on the relation 
between number of molecules and volume 
of gases. 

Avogadro's Law: Equal volumes of 
all gases under the same conditions of 
temperature and pressure contain the 
equal number of molecules. 

Importance of Avogadro's law: This 
law plays an important role in 

(a) deducing atomicity of gases and 

(b) establishing the relation between 
vapour density and molecular mass. 

10.2.1. Atomicity 

The number of atoms present in one 
molecule of an element is called the 
atomicity of an element. 

Depending upon the number of atoms 
in one molecule of an element, molecules 
are classified into monoatomic, diatomic, 
triatomic, and poly atomic molecules. 

For any homo atomic molecule atomicity 
can be deduced using the formula 

Molecular Mass 

Atomicity = 

Atomic mass 

Avogadro's law enables us to change 

over directly from a statement about volume 

of gases to a statement about molecules 

of gases and vice-versa. 



ATOMS AND MOLECULES 




MORE TO KNOW 



Isotopes =^ These are the atoms 
of same element with same atomic 
number (Z) but different mass 
number (A), example (Clf-,,Clll) 

Isobars =^ These are the atoms of 
the different element with same mass 
number but different atomic number, 
example f>4r^^^, Caf^) 

Isotones =^ These are the 

atoms of different elements 

with same number of neutrons 
example : (Cf,N'p 



MORE TO KNOW 







Atomicity 


No. of 
atoms per 
molecule 


Eg 


Monoatomic 


1 


Helium (He) 
Neon (Ne) 
Metals 


Diatomic 


2 


Hydrogen H^ 
Chlorine Cl^ 


Triatomic 


3 


Ozone (O3) 


Polyatomic 


>3 


phosphorous P^ 
Sulphur Sg 





e.g., 



N.+ 



O. 



-^ 



2 NO 



Nitrogen Oxygen Nitric oxide 
(1 Vol) (1 Vol) (2 Vols) 

After applying Avogadro's law, the 
equation becomes 



K 



O. -^ 



1 Molecule 1 Molecule 



2 NO 
2 Molecules 




Avogadro an Italian Scientist 

(1766 - 1856) He was the one to 
propose that volume of a gas at a 
given temperature and pressure 
is proportional to the number of 
particles. 



TEST YOUR 
UNDERSTANDING SKILL 



1. Find the atomicity of chlorine if 
its atomic mass is 35.5 and its 
molecular mass is 71 

2. Find the atomicity of ozone if 
its atomic mass is 16 and its 
molecular mass is 48 



It is found that two molecules of nitric 
oxide contains 2 atoms of nitrogen and 
2 atoms of oxygen. 

These two atoms of nitrogen and the two 
atoms of oxygen should have come from 
1 molecule of nitrogen and 1 molecule of 
oxygen, respectively. 




Hence, nitrogen and oxygen are called 
diatomic molecules and are written as 
N^ and O2. 

This proves that, atomicity of nitrogen 
is 2 and the atomicity of oxygen is 2 

Thus Avogadro's hypothesis is used in 
the deduction of atomicity of elementary 
gases. 

10.2.2. To establish the relationship 
between vapour density and 
relative molecular mass of a 
gas 

i. Relative Molecular Mass: It is defined 
as the ratio of the mass of 1 molecule 
of the gas or vapour to the mass of 
1 atom of hydrogen. 

Relative molecular mass of a gas = 
Mass of Imolecule of the gas or vapour 

Mass of 1 atom of hydrogen 

ii. Vapour Density (V.D): It is defined 
as the ratio of the mass of a certain 
volume of the gas or vapour to the 
mass of the same volume of hydrogen 
at the same temperature and pressure. 



V.D = 



Mass of 1 volume of gas or vapour 



V.D = 



Mass of 1 volume of hydrogen 
Applying Avogadro's Law, 

Mass of 1 molecule of gas or vapour 



Mass of 1 molecule of hydrogen 



V.D- 



Since hydrogen is diatomic, 
Mass of 1 molecule of gas or vapour 



Multiplying both sides by 2, we get 

Mass of 1 molecule of gas or vapour 

2xV.D= 

Mass of 1 atom of hydrogen 

2 X V.D = relative molecular mass of a gas 

or vapour 

2xVapour density = Relative molecular 

mass 

How to arrive at the value of GRAM 
MOLAR VOLUME (CMV) 

GRAM MOLAR MASS 

GMV = 

DENSITY OF GAS AT STP 

To find the value of 

GMMofO^ 
GMV OF OXYGEN = 



DENSITY OF O. 



= 32/1.429 
= 22.4 lit 
Therefore GMV = 22.4 litre at STP 



MORE TO KNOW 



Gay-Lussac's law of combining 
volumes of gases 

Whenever gases react, they do so 
in volumes which bear a simple ratio 
to one another, and to the volumes 
of the gaseous products, provided, 
all the volumes are measured 
under the same conditions of 
temperature and pressure. 



2 X Mass of 1 atom of hydrogen 



10.2.3. Applications of Avogadro's 
law 

1. It is used to determine the atomicity of 
gases. 



ATOMS AND MOLECULES 




2. It is helpful in determining the molecular 
formula of gaseous compound. 

3. It establishes the relationship between 
the vapour density and molecular mass 
of a gas. 

4. It gives the value of molar volume of 
gases at STP. Molar Volume of a gas 
at STP=22.4 lit (or) 22400 cml 

5. It explains Gay Lussac's law effectively. 

10-3- ATOMS AND MOLECULES 

Atoms and molecules are the 
building blocks of matter. 



10.3.1. Atom: It is the ultimate 
particle of an element which may or may 
not have independent existence. The 
atoms of certain elements such as 
hydrogen, oxygen, nitrogen, etc. do 
not have independent existence 
whereas atoms of helium, neon, argon, etc. 
do have independent existence. 
All elements are composed of 
atoms. 

10.3.2. Molecule: A molecule is the 
simplest structural unit of an element (or) 
a compound which contains one (or) more 





Name the elements and find their 
number in one molecule of a) Nitrogen 
b) Water c) Ammonia d) Sulphuric 
acid. 



atoms. It retains the characteristics of an 
element. 

A molecule can exist freely and it is a 
combined form of bonded units whereas 
an atom is a singular smallest form of non 
bonded unit. 

10.3.3. Differences between atom 
and molecule: 



Atom 


Molecule 


An atom is the 


A molecule is the 


smallest 


smallest 


particle 


particle of an 


of 


element or 


an element. 


a compound. 


An atom is a 


A molecule is a 


non bonded 


bonded entity 


entity 




An atom may 


A molecule can 


or may not 


exist freely 


exist freely 





Fig 10.2 Molecule of water 



Molecules are of two types, namely 
homo atomic molecules and hetero atomic 
molecules. 

1. Homo atomic molecules 

These are the molecules which are 
made up of atoms of the same element. 




Most of the elementary gases consist of 
homo atomic molecules. For example 
hydrogen gas consists of two atoms 
of hydrogen (H^). Similarly oxygen gas 
consists of two atoms of oxygen (O2). In 
accordance with the number of atoms 
present in these molecules they are 
classified as monoatomic, diatomic, 
triatomic or poly atomic molecules showing 
that they contain one, two, three, or more 
than three atoms respectively. 

The molecules are made up of atoms 
of different elements. They are also classified 
as diatomic, triatomic, or polyatomic 
molecules depending upon the number of 
atoms present. Hp, NH3, CH^, etc., are the 
examples for hetero atomic molecules. 

lOA RELATIVE ATOMIC MASS 
(RAM) 

10.4.1. Definition (based on 
hydrogen scale) 

The relative atomic mass of an element 



RAM = 



Mass of 1 atom of an element 
Mass of 1 atom of hydrogen 



is the ratio of mass of one atom of the 
element to the mass of one atom of 
hydrogen taken as one unit. 

10.4.2. Definition (based 
on carbon scale) 



RAM=j 



Mass of 1 atom of an element 



Relative atomic mass of an element is 
the ratio of mass of one atom of element 
to the 1/12^^ part of mass of one atom of 
carbon. 

Relative atomic mass is a pure ratio 
and has no unit. If the atomic mass of an 
element is expressed in grams, it is known 
as gram atomic mass. 

e.g., 

Gram atomic mass of hydrogen = 1g 
Gram atomic mass of carbon = 12g 
Gram atomic mass of nitrogen = 14g 
Gram atomic mass of oxygen = 16g 
Gram atomic mass of sodium = 23g 

Atomic mass is expressed in atomic 
mass unit (amu). One atomic mass unit 
is defined as 1/12**^ part of the mass of 
one atom of carbon. 

10-5- RELATIVE MOLECULAR 
MASS(RMM) 

10.5.1. Definition (based 

on hydrogen scale) 



Mass of 1 molecule of an element / cx)mpound 



RMM = 



Mass of 1 atom of hydrogen 



^ th part of the mass of one atom of carbon RM M = 



The relative molecular mass of an 
element or a compound is the ratio of 
mass of one molecule of the element or 
a compound to the mass of one atom of 
hydrogen. 

10.5.2. Definition (based 
on carbon scale) 

Mass of 1 molecule of an element / compound 



L th part of the mass of one atom of carbon 



12 



ATOMS AND MOLECULES 




The relative molecular mass of an 
element or a compound is the ratio of 
mass of one molecule of the element or a 
compound to the mass of 1/12 th part of 
mass of one atom of carbon. 

Relative molecular mass is a pure ratio 
and has no unit. If the molecular mass of 
a given substance is expressed in gram, it 
is known as gram molecular mass of that 
substance. 

Molecular mass is the sum of atomic 
masses. 



Gram molecular mass calcula- 
tions to test your numerical skill 



1 . Find the gram molecular mass of 

water (Hp) 
calculation 

2(H) = 2x1=2 

1(0) = 1 X 16 = 16 



18 



. . Gram molecular mass of H20= 18g 

2. Find the gram molecular mass of carbon 
dioxide (CO^) 

1(C) = 1 X 12 = 12 

2(0) = 2 X 16 = 32 

Gram molecular mass of CO2 = 44 g 

10-6- MOLE CONCEPT 

While performing a reaction, to know the 
number of atoms (or) molecules involved, 
the concept of mole was introduced. The 
quantity of a substance is expressed in 
terms of mole. 



Shown here in Fig. 10.3 are one 
mole quantities of each of the following 
materials: (clockwise from top left) 180g 
of acetylsalicylic acid (aspirin), 18.0g of 
water, 342g of sucrose (table sugar), 201g 




Fig. 10.3 Mole in various forms 

of mercury, 55. 9g of iron, 58. 5g of sodium 
chloride (table salt), and 254g of iodine. 

10.6.1. Definition of mole 

Mole is defined as the amount of 
substance that contains as many specified 
elementary particles as the number of 
atoms in 12g of carbon-12 isotope. 

One mole is also defined as the amount 
of substance which contains Avogadro 
number (6.023 x 10^^) of particles. 



Avogadro number: Number of atoms or 
molecules or ions present in one mole of 
a substance is called Avogadro number. 
Its value is 6.023 x lO^^. 




Therefore, one mole of any substance 
contains Avogadro number of particles. The 
particles may be atoms, molecules, ions etc.. 

For eg. one mole of oxygen atoms 
represents 6.023 x 10^^ atoms of oxygen 
and 5 moles of oxygen atoms contain 
5x 6.023x10^2 atoms of oxygen. 

To find the number of moles, the 
following formulae are useful 



Number of moles = 
Number of moles = 
Number of moles = 
Number of moles = 



Mass 



atomic mass 

Mass 
molecular mass 

No. of atoms 
6.023 X 10"" 

No. of molecules 
6,023 X 10'^ 



WATCH OUT ! 

It may be noted that while using the 
term mole it is essential to specify 
the kind of particles involved. 

10.6.2. Problems (based on mole 
concept) 

1. When the mass of the substance Is 
given: 

K. . r . given mass 

Number of moles = 



atomic mass 
a. Calculate the number of moles in 
i) 81g of aluminium ii) 4. 6g sodium 
iii) 5.1g of Ammonia iv) 90g of water 
v) 2g of NaOH 

given mass _ 81 
" 27 



Number of moles = 



atomic mass 
= 3 moles of aluminium 



FOLLOW UP: Find the number of moles 
for remaining problems given above. 

b. Calculate the mass of 0.5 mole of iron 

Solution: mass = atomic mass x number 
of moles 

= 55.9 X 0.5 = 27.95 g 

FOLLOW UP: Find the mass of 2.5 mole 
of oxygen atoms 

Mass = molecular mass x number of 
moles 

2 . Calculation of number of particles when 
the mass of the substance Is given: 

Number of particles = 

Avogadro number x given mass 



gram molecular mass 

a. Calculate the number of molecules in 
llg of CO2 

Solution: gram molecular mass of 
CQ^ = 44g 



Number, of molecules = 



6.023x1023x11 



44 



= 1.51 X 10^2 molecules 

FOLLOW UP: Calculate the number of 
molecules in 360g of glucose. 

3. Calculation of mass when number of 
particles of a substance Is given: 

Mass of a substance 

gram molecular mass x number of particles 

6.023 X 10^3 
a. Calculate the mass of 18.069 x lO^^ 
molecules of SO^ 

Sol: Gram molecular mass SO = 64g 



ATOMS AND MOLECULES 




Mass of SO. 



64 X 18.069 X 1023 



6.023 X 1023 



= 192g 



b. Calculate the mass of glucose In 
2 X 10^4 molecules 
Gram molecular mass of glucose = 180g 

Mass of glucose 

180 X 2 X 1024 

= = 597.7g 

6.023 X 1023 

FOLLOW UP: Calculate the mass of 
12.046 X 1023 molecules in CaO. 

4. Calculation of number of moles when 
you are given number of molecules: 

Number of molecules 

Number of moles = 

Avogadro Number 



3.0115 X 1023 

= = 0.5 moles 

6.023 X 1023 

b. Calculate number of moles In 12.046x IO22 
atoms of copper 

Number of moles of atoms 

Number of atoms 



Avogadro Number 
12.046 X 1022 



6.023X 1023 



= 0.2 moles 



FOLLOW UP: Calculate the number of 
moles In 24.092 x IO22 molecules of water. 



MORE TO KNOW 



Molar volume: Volume occupied by 
one mole of any gas at STP is called 
molar volume. Its value is 22.4 litres 

22.4 litres of any gas contains 
6.023 X 10^3 molecules. 




1. 162.4 g of FeCh 

2.159.6gofCuS04 

3. 27g ofAl 

4.56gofFe 

5.58.5gofNaCI 

6.32gofS 

7.12gofC 

8.200.6gofHg 



Fig. 10.4 More illustrations for mole in various forms 




EVALUATION 

PART A 

1. From the given examples, form the pair of isotopes and the pair of isobars 

Ar40 P|35 Po40 p|37 

18^' ' 17^' ' 20^"^ ' 17^' 

2. Molecular mass of nitrogen is 28. Its atomic mass is 14. Find the atomicity of 
nitrogen. 

3. Gram molecular mass of oxygen is 32g. Density of oxygen is 1 .429g/cc. Find the 
gram molecular volume of oxygen. 

4. 'Cr represents chlorine atom, 'CI2' represents chlorine molecule. 
List out any two differences between atoms and molecules. 

5. Calculate the gram molecular mass of water from the values of gram atomic mass 
of hydrogen and of oxygen. 

Gram atomic mass of hydrogen = 1g 

Gram atomic mass of oxygen = 16g 

6. One mole of any substance contains 6.023 x 10^^ particles. 

If 3.0115 X 10^^ particles are present in CO2. Find the number of moles. 

PART B 

1. Modern atomic theory takes up the wave concept, principle of uncertainty and 
other latest discoveries to give a clear cut picture about an atom. State the 
findings of modern atomic theory. 

2. You are given the values of mass of one volume of oxygen gas and the mass of 
one volume of hydrogen. By applying Avagadro's law how will you establish the 
relation between vapour density and molecular mass of a gas? 

3. Calculate the number of moles in 

a. 12.046 X 10^3 atoms of copper 

b. 27.95g of iron 

c. 1.51 X 10^3 molecules of CO^ 

FURTHER REFERENCE : 

BOOKS: 1 . Physical Chemistry : Puri and sharma - Vishal 
publications 

2. Inorganic Chemistry : RL. Soni - S.Chand publication 

WEBSITE : www.ehow.com/atomsandmolecules 

www.chem4kids.com/tag/atomsandmolecules 



Chapter 






CHEMICAL 
REACTIONS 



11. Chemical Reactions 



All living beings bom in this beautiful 
world have their own life styles. Have you 
observed and analyzed your daily life from 
the view point of a chemist? Chemical 
reactions happen around us all the time and 
even in our body. 

Any change can be classified as 
physical change and chemical change. 
Physical changes can be easily reversed 
but, it is not easy to reverse a chemical 
change. What is the reason? In chemical 
changes, new substances are formed 
and it is difficult to regenerate the original 
substances. Chemical changes are more 
permanent than physical changes. All 
chemical changes are accompanied by 
chemical reactions. 

How do we come to know that a 
chemical reaction has taken place? Let 
us perform some activities to find out the 
answer to this question. 



ACTIVITY 11.1 



• Look at the new silver anklet of 
your mother or sister 

• Note the colour of the anklet 

• Observe the colour of an old anklet 

• What change do you observe? 



The lustrous white colour of the silver 
anklet slowly changes into slightly black 
colour. That is, silver anklet has got 




Fig. 11.1 Silver Anklet 

tarnished. Can you guess the reason 
behind it? 

It is due to the formation of silver sulphide 
(Ag^S), as a result of the reaction between 
silver and hydrogen sulphide in the air. 



ACTIVITY 11.2 



• Take lead nitrate solution in a 
beaker 

• Take potassium iodide solution 
in a test tube. (Both solutions are 
colourless) 

• Add potassium iodide solution 
slowly to the lead nitrate solution 

• What do you observe? 



I CHEMICAL REACTIONS 



u 



You observe a deep yellow precipitate, 
don't you? 




Fig. 11.2 Yellow precipitate of lead iodide. 
It is lead iodide (Pbl^). 



ACTIVITY 11.3 



• Take 5g of calcium oxide (quick 
lime) in a beaker 

• Add water to it slowly 

• Touch the beaker 



What do you feel? 



Do you feel hot? Let us see what 
happens. 

Calcium oxide reacts with water to 
produce slaked lime (calcium hydroxide). 
This reaction is exothermic and will 
be accompanied by hissing sound 
and bubbles leading to the release of 
considerable amount of heat. 



ACTIVITY 11.4 



• Take a pinch of calcium carbonate 
powder in a test tube 

• Add dilute hydrochloric acid 

• Note the changes in the test tube 
carefully 



Do you observe any brisk 
effervescence? It is due to the evolution 
of carbon dioxide gas. 




Fig. 11.2 Reaction of calcium 
carbonate with dil.HCI 

These are some of the common 
observations in a chemical reaction. From 
the activities that we have discussed, it 
is clear that chemical reactions will bring 
about a permanent change resulting in 
the formation of new product(s). 

The substances taking part in the 
reaction are known as reactants and 
those formed as a result of the reaction 
are called products. 



MORE TO KNOW 



A solution of slaked lime produced 
in the Activity 11.3 is used for white 
washing. Calcium hydroxide reacts 
slowly with carbon dioxide in air to 
form athin layer of calcium carbonate 
on the walls. Calcium carbonate is 
formed after two to three days of 
white washing and gives a shiny 
finish to the walls. It is interesting to 
note that the chemical formula for 
marble is also CaCO. 



II.ITYPES OF CHEMICAL 
REACTIONS 

Since there are numerous chemical 
reactions, the study of these reactions 
can be made easier by classifying them. 
All the chemical reactions are classified 
into six broad categories depending on 
the way the product formed. 

Let us see the different types of 
classifications of chemical reactions. 

1. COMBINATION REACTION 



© 




B 




A[ B 



A combines with B to form a new 
product AB. It is the simple representa- 
tion of combination reaction. 



ACTIVITY 11.5 



Take a clean piece of magnesium 
ribbon 

Hold the ribbon with a pair of tongs 

Burn it in air using a burner 
(keeping Mg ribbon as far as 
possible from your eyes) 

Collect the ash 




In the above activity, magnesium 
combines with oxygen to form a single 
product, magnesium oxide. Such a 
reaction in which a single product 
formed from two or more reactants is 
known as combination reaction. 

2Mg + O2 ^ 2MgO 

Repeat "Activity 11.3". This reaction 
is also an example for COMBINATION 
REACTION. Attempt to write the equation 
yourself. 



Let us discuss some more examples of 
combination reactions. 

• Combustion of coal 

• Combustion of hydrogen 



2H, + 0, 



2Hp 



2 DECOMPOSITION REACTION 



(*® 



®* 



® 



AB splits into A and B. It is the 
representation of decomposition reaction. 



ACTIVITY 11.6 



• Take about 2 g of copper carbonate 
powder in a dry test tube 

• Note the colour of copper carbonate 

• Heat the test tube over the flame 

• Observe the change after heating 



Fig. 11.4 Burning of Mg ribbon 



I CHEMICAL REACTIONS 



u 




2. Decomposition of ammonium 



Fig. 11.5 Heating tine test tube 
containing copper carbonate 



dichromate 



MORE TO KNOW 



At very high temperature, ammonium 
dichromate decomposes immediately 
to green vapours which gets released 
along with the steam. It seems as if 
a volcano erupts and is termed as 
chemical volcano. 



Change of colour from green to black is 
observed. This is due to the decomposition 
of copper carbonate to copper (II) oxide. 
CuO + CO^t 



CuC03^ 



ACTIVITY 11.7 



• Take lead nitrate in a test tube 

• Heat it over the flame 



Observe the changes 



Liberation of a reddish brown gas (NO^) 
is observed. This is because of the 
decomposition of lead nitrate into lead 
oxide, nitrogen dioxide and oxygen. 



2Pb(N03)2 ^ 2PbO + 4N02t + O^T 

From the above two activities (11.6 
and 11.7), It can be noted that a single 
compound breaks down to produce 
two or more substances. Such type 
of reaction is called decomposition 
reaction. 

Someotherexamplesfordecomposition 
reaction: 

1. Decomposition of lime stone 
CaC03^ CaO + CO A 



3- DISPLACEMENT REACTION 

®.®3^(a©.(b) 

In the reaction between A and BC, A 
displaces B from BC to form AC. This 
shows that A is more reactive than B. 



ACTIVITY 11.8 



Take 20 ml of copper sulphate 
solution in a beaker 

Drop an iron nail into the beaker 

Leave it for few days 

Observe the colour of the copper 
sulphate solution and the iron nail 



Copper 

sulphate 

solution 


^ 


-^ 










Co 


)er 


-^ ^ 


Ferrous 
sulphate 



Fig. 11.6 Iron displaces copper from copper 
sulphate solution 



Blue colour of the copper sulphate 
solution changes into green colour and the 
iron nail acquires a brownish look. It is a 
noticeable change. Is it not? This change 
confirms that iron is more reactive than 
copper. The following chemical reaction 
takes place in this activity. 



Fe + CuSO. 



FeSO, + Cu 

4 



In this reaction, iron displaces copper 



from CuSO^ solution. 



Repeat "Activity 11.8" but use zinc 
rod instead of an iron nail. What colour 
changes do you observe on the rod and in 
the solution? Write the chemical equation. 



Other example: 
Pb + CuCI. 



PbCi^+Cu 



Lead can displace copper from its 
salt solutions. Can copper displace zinc 
or lead from their salt solutions? No, 
because copper is less reactive than zinc 
and lead. 

The reaction in which, a more 
reactive element displaces a less 
reactive element from its compound is 
called displacement reaction. 

4. DOUBLE DECOMPOSITION 
REACTION (DOUBLE 
DISPLACEMENT REACTION) 



ACTIVITY 11.9 



Take 5ml of sodium sulphate 
solution in a test tube 

In another test tube, take 5ml of 
barium chloride 

Mix both the solutions 

What do you observe? 




Fig. 11.7 Formation of barium suiphate 

You will observe formation of a white 
substance, which is insoluble in water. 
The insoluble substance formed is known 
as precipitate. Any reaction that produces 
a precipitate is called a precipitation 
reaction. The formed white precipitate 
of barium sulphate, is due to the reaction 
of SO/- and Ba^^ ions. The other product 
formed is sodium chloride. 



A(B) + 



(a]^ + ^^ Na^SO^ + BaCI^ 



BaSO J + 2NaCI 



In the reaction between AB and CD, 
both the reactants decompose to form 
AD and CB through the rearrangement 
of ions. 



Repeat "Activity 11.2" for double de- 
composition reaction. Attempt to write the 
equation by yourself. 



I CHEMICAL REACTIONS 



u 



Double decomposition reaction is 
any reaction in which exchange of ions 
between two reactants occur, leading to 
the formation of two different products. 

Other example : 



CuSO^ + H^S 



CuSi + H,SO, 



5- OXIDATION AND REDUCTION 

We are all aware of the fact that 
oxygen is the most essential element 
for sustaining life. One can live without 
food or even water for a number of days, 
but not without oxygen. In our daily life 
we come across phenomena like fading 
of the colours of the clothes, burning of 
combustible substances like cooking gas, 
wood and coal, and also rusting of iron 
articles. All such processes fall in the 
category of a specific type of chemical 
reaction called oxidation - reduction 
reaction (redox reaction). A large number 
of industrial processes like electroplating, 
extraction of metals like aluminium, are 
based upon the redox reaction. 



Oxidation: 

A chemical reaction which involves 
addition of oxygen or removal of 
hydrogen or loss of electron(s) is 
called as oxidation. 
2Mg + 02^2MgO (addition of oxygen) 

H^S + Br^ -^ 2HBr + S (removal of hydrogen) 

Fe^"" -^ Fe^"" + e" (loss of electron) 
Reduction: 

A chemical reaction which involves 
addition of hydrogen or removal of 
oxygen or gain of electron(s) is called 
as reduction. 

2Na + H2 ^ 2NaH (addition of hydrogen) 
CuO + H2 ^ Cu + H2O (removal of oxygen) 

Fe^"" + e" ^ Fe^"" (gain of electron) 
Redox reaction: 

A chemical reaction in which 
oxidation and reduction take place 
simultaneously is called redox reaction. 
Zn + CuSO, ^ Cu + ZnSO, 

4 4 

Attempt to write any other redox reaction 







Reduction 


















1 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^r 




^ 








Copper (II) oxide 




Copper 






Oxidation 





Fig. 11.8 Redox reaction 



During the conversion of copper(ll) 
oxide to copper, the copper(ll) oxide is 
losing oxygen and is being reduced. The 
hydrogen is gaining oxygen and is being 
oxidised. In other words, one reactant 
gets oxidised while the other gets reduced 
during the reaction. Such reactions are 
called oxidation - reduction reactions or 
redox reactions. 



Oxidation is 

Gain of oxygen 
Loss of hydrogen 
Loss of electron(s) 



Reduction is 

Loss of oxygen 
Gain of hydrogen 
Gain of electron(s) 



Oxidation and reduction always takes 
place together, so the reaction is called 
redox reaction. 



DON'T FORGET 

Loss of electron is oxidation. 

Gain of electron is reduction. 

The term LEO, GER will help you to 
remember. 



MORE TO KNOW 



Oxidation also has damaging effects 
on food and eatables. When food 
containing fat and oil is left as such 
for a long time, it becomes stale. The 
stale food develops bad taste and 
smell. This is very common in curd 
or cheese particularly in summer. 
Oils and fats are slowly oxidised to 
certain bad smelling compounds. 



6. EXOTHERMIC AND ENDOTHERMIC 
REACTIONS 

During chemical reactions one of the 
most common change is a change 
in temperature. When detergent is 



dissolved in water to wash clothes, heat 
is given out. When glucose is kept on 
our tongue, a chilling effect is felt. During 
these processes, heat is either given out 
or absorbed from the surroundings. In 
the same way, in most of the chemical 
reactions, energy is either taken up or 
given out. 

a. Exothermic reactions 

The chemical reactions which 
proceed with the evolution of 
heat energy are called exothermic 
reactions. 



N^ + 3H2 



2NH +Heat 



All combustion reactions are 
exothermic. Heat energy is liberated as 
the reaction proceeds. 
b. Endothermic reactions 

The chemical reactions which 
proceed with the absorption of 
heat energy are called endothermic 
reactions. 



2NH + Heat 



N. + 3H, 



11-2 RATE OF THE CHEMICAL 

REACTION 
Rate of the chemical reaction is defined 
as change in concentration of any one 
of the reactants or products per unit time. 

Consider the reaction 

Rate of the reaction is given by 

d[A] d[B] 

Rate = - = + 

dt dt 

[A] - concentration of reactant A 

[B] - concentration of product B 

- ve sign indicates decrease in con 
centration of A with time. 



I CHEMICAL REACTIONS 



u 



+ ve sign indicates increase in con- 
centration of B with time. 

11.2.1 FACTORS INFLUENCING 

THE RATE OF THE CHEMICAL 
REACTION 

1. NATURE OF THE REACTANTS 



ACTIVITY 11.10 



• Take magnesium ribbon in two test 

tubes A and B 

• Add hydrochloric acid to test tube A 

• Add acetic acid to test tube B 

• Observe the changes in two test 
tubes 



Magnesium ribbon reacts with both 
hydrochloric acid and acetic acid but 
reaction is faster in hydrochloric acid 
than in acetic acid. Do you know why? 
Hydrochloric acid is more reactive 
than acetic acid. It shows that nature 
of the reactant influences the rate 
of the reaction. 



OF THE 



2. CONCENTRATION 
REACTANTS 



ACTIVITY 11.11 



• Take 3g of granulated zinc in the 
test tube A and B 

• Add 5 ml of 1 M hydrochloric acid 
in test tube A 

• Add 5 ml of 2 M hydrochloric acid 
in test tube B 



Granulated zinc reacts with both 1M 
hydrochloric acid and 2M hydrochloric 
acid, the rate of evolution of hydrogen 
gas is more from the test tube B than 
from the test tube A. This is because, 2M 
hydrochloric acid is more concentrated 
than 1 M hydrochloric acid. That is, greater 
the concentration of the reactant, 
greater will be the rate of the reaction. 



OF THE 



3- SURFACE AREA 
REACTANTS 



ACTIVITY 11.12 



• Take powdered calcium carbonate 
in beaker A 

• Take marble chips (calcium 
carbonate) in beaker B 

• Add hydrochloric acid in both 
beakers A and B 



Observe the changes 



Observe the changes 



Powdered calcium carbonate reacts more 
quickly with hydrochloric acid than marble 
chips. What is the reason?. 

Powdered calcium carbonate offers 
large surface area for the reaction to 
occur at a faster rate. This shows that 
greater the surface area, greater is the 
rate of the reaction. 

4. TEMPERATURE 



ACTIVITY 11.13 



• Take 3g of marble chips in a beaker 

• Add 5 ml of 1 M hydrochloric acid 

• Observe the changes 

• Heat the beaker 

• Observe the changes 



Calcium carbonate present in marble 
chips react slowly with hydrochloric 
acid at room temperature and evolves 
carbon dioxide at slower rate, whereas on 
heating, the evolution of carbon dioxide is 
made faster.This shows that increase in 
temperature increases the rate of the 
reaction. 

5. CATALYST 



ACTIVITY 11.14 



Take potassium chlorate in a test 
tube 

Heat the test tube 

Observe what happens 

Add manganese dioxide as a 
catalyst 

Observe the changes 



When potassium chlorate is heated, 
oxygen is evolved very slowly whereas 
after the addition of manganese dioxide 
to the reactant, oxygen is liberated at a 
faster rate. This shows that manganese 
dioxide acts as a catalyst and 
influences the rate of the reaction. 

GROUP ACTIVITY 

• From dawn to dusk observe any 
10 chemical changes taking place 
around you and classify them 

• Prepare volcano using ammonium 
dichromate (vigorous) 

• Prepare volcano using baking 
soda (silent) 



MORE TO KNOW 



A substance which alters the rate of 
the reaction without undergoing any 
change in mass and composition is 
known as catalyst. 



ACIDS, BASES AND SALTS 



Nivi : 


Hai Vini, you look tired. 




Take this fresh lime juice. 1 


Vini : 


No, it has sour taste. ^ 


Nivi : 


Do you know why is it sour? 


Vini : 


Sorry, 1 have no idea at all. 


Nivi : 


It is due to the presence 




of acid. Ok let's get set to 


^ 


learn about this. 1 



Acids, bases and salts are used in 
everyday life. Let it be a fruit juice or a 
detergent or a medicine. They play a key 
role in our day-to-day activities. Our body 
metabolism is carried out by means of 
hydrochloric acid secreted in our stomach. 

11.3. ACIDS 



Acid is a substance which furnishes 
H^ ions or H30^ ions when dissolved in 
water. Acids have one or more replacable 
hydrogen atoms. The word acid is derived 
from the Latin name 'acidus' which means 
sour taste. Substances with 'sour taste' 
are acids. Lemon juice, vinegar and grape 
juice have sour taste, so they are acidic. 
They change blue litmus to red. They are 



I CHEMICAL REACTIONS 



u 




Fig. 11.9 Acid solution turns blue 
litmus paper red 

colourless with phenolphthalein and pink 
with methyl orange. Many organic acids 
are naturally present in food items. 

11-3-1 CLASSIFICATION OF 

ACIDS 

1. Based on their sources : Acids 
are classified into two types namely 
organic acids and inorganic acids. 
Organic acids:- Acids present in 
plants and animals (living beings) 
are organic acids eg. HCOOH, 
CH3COOH (Weak acids). 

Inorganic acids:- Acids from rocks 
and minerals are inorganic acids or 

mineral acids eg. HCI, HNO3, H^SG^ 
(Strong acids). 

2. Based on their basicity 

Monobasic acid: - It is an acid which 
gives one hydrogen ion per molecule 
of the acid in solution eg. HCI, HNO3 
Dibasic acid:- It is an acid which gives 



Source 


Acid present 


Apple 


Malic acid 


Lemon 


Citric acid 


Grape 


Tartaric acid 


Tomato 


Gxalic acid 


Vinegar (food 


Acetic acid 


preservative) 




Curd 


Lactic acid 




What is the acid present in it? 

two hydrogen ions per molecule of the 
acid in solution e.g., H^SG^, H2CG3 

Tribasic acid:- It is an acid which gives 
three hydrogen ions per molecule of 
the acid in solution. e.g.,H3PG4, 



MORE TO KNOW 



For acids, we use the term basicity 
which means the number of replaceable 
hydrogen atoms present in one molecule 
of an acid. For example acetic acid has 
four hydrogen atoms but only one can 
be replaced. Hence it is monobasic. 



3. Based on ionisation 

Acids are classified into two types 
based on ionisation. 

Strong acids:- These are acids which 
ionise completely in water eg.HCI 

Weak acids:-These are acids 
which ionise partially in water eg. 
CH3COOH 

4. Based on concentration:- Depending 
on the percentage or amount of acid 
dissolved in water acids are classified 
into concentrated acid and dilute acid. 

Concentrated acid:- It is an acid 
having a relatively high percentage 
of acid in its aqueous solution. 

Dilute acid:- It is an acid having a 
relatively low percentage of acid in 
aqueous solution. 



MORE TO KNOW 



Care must be taken while mixing any 
concentrated mineral acid with water. 
The acid must always be added 
slowly to water with constant stirring. 
If water is added to a concentrated 
acid the large amount of heat is 
generated which may cause burns. 
The mixture splashes out of the 
container. 



ACTIVITY 11.15 



Take 5 g of zinc granules in a 
test tube 

Add 10 ml of dilute hydrochloric 
acid through thistle funnel 

During the course of addition, 
what do you observe? 




11.3-2 CHEIVIICAL PROPERTIES OF 
ACIDS 

1 REACTION OF IVIETALS WITH ACID 



Fig. 11.10 Reaction ofZn granules witli dilute HCI 

Note that zinc reacts with dilute 
hydrochloric acid to form zinc chloride 
and hydrogen gas. 

Zn + 2HCI -^ ZnCi^ + H^T 

When a burning candle is brought near 
the bubble containing hydrogen gas, the 
flame goes off with a 'pop'ing sound. This 
confirms that metal displaces hydrogen 
from the dilute acid. (Hydrogen gas burns 
with a 'pop'ing sound) 

Metal + Acid -^ Salt + Hydrogen 

Another example 

Mg + H^SG.^MgSG. + H^T 



MORE TO KNOW 



• All metals do not liberate hydrogen 
gas on reaction with acids, eg., Ag,Cu. 

• Lime stone, chalk and marble are 
different physical forms of calcium 
carbonate. They react with acids 
giving corresponding salt, carbon 
dioxide and water. 



I CHEMICAL REACTIONS 



u 



REACTION OFMETALCARBONATE 
AND METAL BICARBONATE WITH 
ACIDS 



ACTIVITY 11.16 



• Take two test tubes, label them as 
I and II 

• Take small amount of washing soda 
(Na2C03) in test tube I and small 
amount of baking soda (NaHCOg) 
in test tube II 

• Add dilute hydrochloric acid to both 
the test tubes 

• What do you observe? 

• Pass the gas produced in each case, 
through limewater[Ca(OH)2] solution 
and record your observations 



From the above activity the reaction 
can be summarized as 



Fig. 11.11 Testing of carbon dioxide 

Test tube I 

Na2C03+ 2 HCI ^ 2 NaCI + H^O + CO^T 

Test tube II 

NaHC03+ HCI -^ NaCI + H^O + CO^T 

When carbon dioxide is passed 
through lime water, it turns milky. 

Ca(0H)2+ CO^^ CaC03 + H^O 

(milky) 



Metal carbonate 

or + Acid 

Metal bicarbonate 



Salt 

+ 

■^ Water 

+ 

Carbon 

dioxide 



Other examples 

MgC03+ 2 HCI -^ MgCI^ + H^O + CO^t 

Mg(HC03)2+ 2 HCI -^ MgCI^ + 2H2O + 200^! 



MORE TO KNOW 



Since metal carbonates and metal 
bicarbonates are basic they react 
with acids to give salt and water with 
the liberation of carbon dioxide. 




3. REACTION OF METALLIC 
OXIDES WITH ACIDS 



ACTIVITY 11.17 



• Take about 2g copper (II) oxide 
in a watch glass and add dilute 
hydrochloric acid slowly 

• Note the colour of the salt 

• What has happened to the copper 
(II) oxide? 




Fig. 11.12 Reaction of copper (ii) oxide witli 
dilute liydrocliloric acid 



The colour changes from black to green. 
This is due to the formation of copper 
(II) chloride in the reaction. Since metal 
oxides are basic, they react with acid to 
form salt and water. 

CuO + 2HCI -^ CuCI^ + H^O 
From the above activity we conclude that 



Salt + Water 



Metallic oxide + Acid 

Another example 
CaO + 2HCI 

4 . ACTION OF ACIDS WITH WATER. 

An acid produces hydrogen ions in water. 



CaCI^ + H^O 



HCI + H^G 



H.O^ + CI" 



Hydrogen ions cannot exist alone, 
but they exist in the form of hydronium 
(HgO^) ions with water. When water is 
absent, the separation of hydrogen ions 
from an acid does not occur. 

11.3.3. USES OF ACIDS 

1. Sulphuric acid (King of chemicals) 
is used in car battery and in the 
preparation of many other compounds. 

2. Nitric acid is used in the production of 
ammonium nitrate which is used as 
fertilizer in agriculture. 

3. Hydrochloric acid is used as cleansing 
agent in toilet. 

4. Tartaric acid is a constituent of baking 
powder. 

5. Salt of benzoic acid (sodium benzoate) 
is used in food preservation. 

6. Carbonic acid is used in aerated 
drinks. 



MORE TO KNOW 



The atmosphere of Venus is made 
up of thick white and yellowish 
clouds of sulphuric acid. Do you 
think life can exist on this planet? 



11.4. BASES 

Base is a substance which releases 
hydroxide ions when dissolved in water. 
It is a substance which is bitter in taste 
and soapy to touch (e.g. Washing soda, 
caustic soda and caustic potash). They 
change red litmus to blue. They are pink 
with phenolphthalein and yellow with 
methyl orange. 




Fig. 11.13 Bases turns red litmus paper blue 

11.4.1. Classification of bases 

1. Based on ionisation 

Strong bases:- These are bases 
which ionise completely in aqueous 
solution eg. NaOH, KOH. 
Weak bases:- These are bases 
which ionise partially in aqueous 
solution eg. NH^H, CaCOH)^ 

2. Based on their acidity 
Monoacidic base:- It is a base 
which ionises in water to give 



I CHEMICAL REACTIONS 



u 



one hydroxide ion per molecule 
eg.NaOH, KOH. 

Diacidic base:- It is a base which 
ionises in water to give two 
hydroxide ions per molecule eg. 
Ca(OH),, MgCOH)^. 

Triacidic base:- It is a base which 
ionises in water to give three 
hydroxide ions per molecule eg. 
AI(OH)3, Fe(OH)3. 



MORE TO KNOW 



The term acidity is used for 
base which means the number 
replaceable hydroxyl groups present 
in one molecule of a base. 



3. Based on the concentration: 

Depending on the percentage 
or amount of base dissolved in 
water, bases are classified as 
concentrated alkali and dilute alkali. 

Concentrated alkali:- It is an alkali 
having a relatively high percentage 
of alkali in its aqueous solution. 

Dilute alkali:- It is an alkali having a 
relatively low percentage of alkali in 
its aqueous solution. 



MORE TO KNOW 



Bases which dissolve in water 
are called alkalies. All alkalies are 
bases, but not all bases are alka- 
lis. NaOH and KOH are alkalies 
whereas AI(OH)3 and Zn(0H)2 are 
bases. 



11.4.2. Chemical Properties of 

Bases 
1. REACTION OF BASE WITH 
METALS 

Zinc reacts with sodium hydroxide 
to form sodium zincate with the 
liberation of hydrogen gas. 

Zn + 2 NaOH -^ Na.ZnO + H,t 



Metal + Base 

Another example 



2 ^2 2' 

Salt + Hydrogen 



2 Al + 2 NaOH + 2 H O ^ 2 NaAlO, + 3 H t 



MORE TO KNOW 



All metals do not react with sodium 
hydroxide eg. Cu,Ag, Or 



2. REACTION OF NON METALLIC 
OXIDES WITH BASES 

Sodium hydroxide reacts with carbon 
dioxide gives sodium carbonate and water. 

2NaOH + CO2 -^ Na2C03 + H^O 

The above reaction confirms that 
Non metallic oxide + Base -^ Salt + Water 
Another example 
Ca(0H)2 + CO2 



CaC03 + H^O 



3. ACTION OF BASES WITH WATER 

Bases generate hydroxide (OH") ions 
when dissolved in water. 

NaOH -^ Na^ + OH" 



4. REACTION OF ACIDS WITH BASES 



ACTIVITY 11.18 



• Indira takes 20 ml of 0.1 N sodium 
hydroxide solution in a conical 
flask and adds few drops of 
phenolphthalein. 

• What colour does she observe? 

• She is adding 20 ml of 0.1 N 
hydrochloric acid solution to 
the above conical flask drop by 
drop. 

• Does she observe any colour 
change in the reaction mixture? 




NaOH solution 



NaOH Solution 

+ 
Phenolphthalein 



Phenolphthalein 
HCI Solution 



In the above activity, Indira observed that 
the effect of a base is nullified by an acid. 

NaOH + HCI -^ NaCI + KO 



Fig. 11.14 Reaction of sodium hydroxide witti 
hydrocliloric acid 

11.4 USES OF BASES 

1. Sodium hydroxide is used in the 
manufacture of soap. 

2. Calcium hydroxide is used in white 
washing the buildings. 

3. Magnesium hydroxide is used as a 
medicine for stomach troubles. 

4. Ammonium hydroxide is used to 
remove grease stains from clothes. 



The above reaction between an acid and 
a base is known as neutralisation reaction. 

Acid + Base -^ Salt + Water 

11.5 IDENTIFICATION OF ACIDS AND BASES 



ACTIVITY 11.19 



Collect lemon juice, washing soda solution, soap solution and soft drinks. 

Take 2 ml of each solution in a test tube and test with a litmus paper or 
indicator. 

What change in colour do you observe with red litmus, blue litmus, 
phenolphthalein and methyl orange? 

Tabulate your observations. 



Sample solution 


Red 
litmus 


Blue 
litmus 


Phenolphthalein 


Methyl 
orange 


Lemon Juice 










Washing soda Solution 










Soap solution 










Soft drinks 











I CHEMICAL REACTIONS 



u 



Same activity can be repeated for dilute 
hydrochloric acid, dilute sulphuric acid, 
sodium hydroxide solution and potassium 
hydroxide solution with the help of your 
teacher. 



INDICATOR 


COLOUR 
IN ACID 


COLOUR 
IN BASE 


Litmus 


Red 


Blue 


Phenolphthalein 


Colourless 


Pink 


Methyl orange 


Red 


fellow 



11.6 pH SCALE 

pH stands for the power of hydrogen 
ion concentration in a solution. pH values 
decide whether a solution is acidic or 
basic or neutral. pH scale was introduced 
by S.P.L. Sorenson. It is mathematically 
expressed as 

For neutral solution [H""] = 10~^M; pH = 7 

For acidic solution [H""] > 10~^M; pH < 7 

For basic solution [H*] < 10~^M; pH > 7 

When OH ions are taken into account 
the pH expression is replaced by pOH 
pOH = -log, JOH-] 



14 1312U10 9 8 76 54 3 21 
p({)H 



pH 

12 3 4 5 6 7 8 9 10 11 12 13 14 

< — Acidic nature increeises •*■ Basic nature increeises — > 
Neutral 

Problems 

1. The hydrogen ion concentration of a 
solution is O.OOIM. What is the pH of the 
solution? 



Solution 

pH = - log,„ [H1 

pH = - log,, (0.001) 

pH = - log,, (10-3) 

= -(-3) log,, 10 [log 10 = 1] 

pH = 3 

2. The hydrogen ion concentration of a 
solution is 1.0 x 10'^ IVI. What is the pH 
of the solution? Predict whether the given 
solution is acidic, basic or neutral. 

Solution 

pH = - log,, [H1 

pH = - log,, (1.0 X 10-3 ) 

pH = - (log„1.0 + log„10-9 ) [ log,, 1 = 0] 

= - (0-9 log,, 10) 
pH = - (0 - 9) = 9 

pH = 9 ie pH >7 

Therefore the given solution is basic. 

3. The hydroxyl ion concentration of a 
solution is O.OOIIVI. What is the pH of the 
solution? 

Solution 

pOH = -log„[OH-] 

pOH = -log,, (10-3) 

pOH = 3 

pH = 14-pOH 

pH = 14-3 = 11 

4. The hydroxyl ion concentration of a 
solution is 1.0 x 10"^ M. What is the pH of 
the solution? 

Solution 

pOH = -log„[OH-] 

pOH = -log,, (1.0 X 10-9) 



pH + pOH = 14 
pH = 14-pOH 



pOH = 9 
pH = 14-pOH 
pH = 14-9 = 5 
11. 6.1 pH paper 

A more common method of measuring 
pH in a scliool laboratory Is by using pH 
paper. pH paper contains a mixture of 
indicators, which gives different colours 
across the entire pH range. pH value of 
the various solutions are given in the table. 



pH 



pH =logio 



log,o[H^] 



I 



H" 



[H^] = 10-"" 
[H^] = l X lO"*^ ;pH = 7 
[H^] = l ^ \0~^ ; pH = 2 
[H^]=l X 10"'^ ; pH= 14 













Solution 


Approximate 
pH 




k 


PK— 




Lemon juice 


2.2-2.4 


L 


^^^j|7I^^ p" 


Tomato juice 


4.1 


Coffee 


4.4-5.5 


Human saliva 


6.5-7.5 


B 


^^i^^^^B 


House hold 
ammonia 


12.0 


T 


^^niftaF" 






Fig. 11.15 pH paper 













ACTIVITY 11.20 



• Take lemon juice, orange juice, 1 M NaOH, 1 M HCI, pure water and vinegar 

• Dip pH paper into these solutions 

• Observe the changes 



SI. No. 


Sample 


Colour of 
pH paper 


Approximate pH 


Nature of 
substance 


1. 


Lemon juice 








2. 


Orange juice 








3. 


IMNaOH 








4. 


IMHCI 








5. 


Pure Hp 








6. 


Vinegar 









I CHEMICAL REACTIONS 



u 



11.6.2 Importance of pH in 
everyday life 

1. pH in human body 

(i) Using pH factor the healthiness of 
our body is predicted. At pH level 
6.9, the body becomes prone to 
viral infections like colds, cough 
and flu. Cancer cells thrive inside 
the body at a pH of 5.5. 

(ii) The pH of a normal, healthy human 
skin is 4.5 to 6. Proper skin pH is 
essential for a healthy complexion. 

(iii) pHofstomach fluid is approximately 
2.0. This fluid is essential for the 
digestion of food. 

(iv) Human blood pH range is 7.35 to 
7.45. Any increase or decrease in 
this value, leads to diseases. The 
ideal pH for blood is 7.4. 

(v) pH of normal saliva ranges 
between 6.5 to 7.5. 

(vi) White enamel coating in our teeth 
is calcium phosphate, hardest 
substance in our body. It does 
not dissolve in water. If pH of 
mouth falls below 5.5, the enamel 
gets corroded. Toothpastes are 
generally basic, and is used for 
cleaning the teeth, can neutralize 
the excess acid and prevent tooth 
decay. 

2. pH in soil 

In agriculture, the pH of soil is very 
important. Citrus fruits require slightly 
alkaline soil, while rice requires acidic soil 
and sugar cane requires neutral soil. 



3. pH in rain water 

pH of rain water is approximately 
7 showing high level of its purity and 
neutrality. If rain water is polluted by SO2 
and NG^, acid rain occurs, bringing the pH 
value less than 7. 

11.7 SALT 

When you say salt, you may think of 
white stuff put on chips. But that is just one 
salt called common salt. There are many 
other salts used in other fields. Salts are 
the products of the reaction between acids 
and bases (see reaction of acids and 
bases), which produce positive ions and 
negative ions when dissolved in water. 

11.7.1 Classification of salts 

1. Normal salts 

A normal salt is obtained by complete 
neutralization of an acid by a base 

NaOH + HCI 

2. Acid salts 

Acid salts are derived by the partial 
replacement of hydrogen ions of an acid 
by a metal. When a calculated amount of 
a base is added to a polybasic acid, acid 
salt is obtained, as follows. 



NaCI + H^O 



NaOH + H^SO^ 
3. Basic salts 



NaHSO^+H^O 



Basic salts are formed by the partial 
replacementofhydroxideionsofadiacidic 
or triacidic base by an acid radical. 

A basic salt may further reacts with an 
acid to give a normal salt. 

Pb(0H)2 + HCI -^ Pb(OH)CI+ H^O 

Diacidic base Basic salt 



4. Double salts 

Double salts are formed by the 
combination of saturated solution of two 
simple salts in equimolar ratio followed by 
crystallization, 
e.g. potash alum 

11-7.2 USES OF SALTS 

Common salt (NaCI) 

It is used in our daily food and as 
preservative. 

Washing soda (Na2C03) 

1 . It is used in softening hard water. 

2. It is used as a cleaning agent for 
domestic purposes. 

Baking soda (NaHC03) 

1 . It is used in nnaking baking powder, 
which is the nnixture of baking soda 
and tartaric acid. Baking powder is 



used to nnake cake and bread soft 
and spongy . 

2. It is an ingredient in antacid. Being 
alkaline, it neutralises excess of 
acid in the stonnach. 

Bleaching powder (CaOCl2) 

1. It is used for disinfecting drinking 
water to make it free from 
microorganisms. 

2. It is used for bleaching cotton and 
linen in the textile industry 

Plaster of parisCCaSO^. lIZHp) 

It is used for plastering fractured bones 
and in making casts for statues 



GROUP ACTIVITY 

Prepare the following salt in 
laboratory 

1. Sodium chloride 

2. Potash alum 



the 



EVALUATION 



PART A 



1. Zn + 2HCI^ZnCl2 + H2t 

The above reaction is an example of 

a) Combinationreaction 

b) Double displacement reaction 

c) Displacement reaction 

d) Decomposition reaction. 

2. A reddish brown coloured element X 
on heating in air becomes black 
coloured compound 'Y'. X and Y 

are and (Cu, CuO / 

Pb, PbO). 



3. A student tested the pH of pure water 
using a pH paper. It showed green 
colour. If a pH paper is used after 
adding lemon juice into water, what 
color will he observe? (Green / Red / 
Yellow) 

4. Chemical volcano is an example of 
(combination reaction / decomposition 
reaction) 

5. When crystals of lead nitrate on heating 

strongly produces a gas and the 

colour of the gas is . 



I CHEMICAL REACTIONS 



u 



6. When aqueous solution of silver nitrate 

and sodium chloride are mixed 

precipitate is immediately formed 
(white / yellow / red). 

7. Zinc can displace aluminium metal 
from aquous solution of aluminium 
sulphate (zinc is more reactive than 
aluminium / aluminium is more reactive 
than zinc ). 

8. To protect tooth decay, we are advised 
to brush our teeth regularly. The nature 
of the tooth paste commonly used is 
in nature. 

9. Vinegar is present in acetic acid. Curd 

contains acid (Lactic acid / 

Tartaric acid). 

lO.pH = - log^Q [H^]. The pH of a solution 
containing hydrogen ion concentration 
of 0.001 M solution is (3/11 / 14) 

PARTE 

ll.What type of chemical reaction takes 
place when i) limestone is heated ii) a 
magnesium ribbon is burnt in air? 

12. The pH values of certain familiar 
substances are given below. 



^^^^plp^^ 


1 pH valu^^H 


Blood 


7.4 


Baking soda 


8.2 


Vinegar 


2.5 


Household 
ammonia 


12 



analyse the data in the table and 
answer the following questions 

a) Which substance is acidic in nature? 

b) Which substances are basic in nature? 

13.Why does the colour of copper sulphate 
change when an iron nail is kept in it? 
Justify your answer. 

14. The hydroxyl ion concentration of a 
solution is 1.0 x 10"^M. What is the pH 
of the solution? 

15. Equal lengths of magnesium ribbons 
are taken in test tubes A and B. 
Hydrochloric acid is added to test 
tube A, while acetic acid is added to 
test tube B. Amount and concentration 
taken for both the acids are same. In 
which test tube reaction occurs more 
vigourously and why? 



FURTHER REFERENCE 
Books: 

1 .Text book of Inorganic Chemistry-P.L. Soni - S.Chand & sons publishers 
2. Principles of Physical Chemistry -B.R. Puri, L.R. Sharma Vishal publishers 
Websites: 

www. ask.com 
www.chem4kids.com 



Chapter 





i 




PERIODIC 

CLASSIFICATION OF 
ELEMENTS 



I PERIODIC CLASSIFICATION 




12. Periodic ciassif ication of elements 



Have you ever visited a library? There 
are thousands of books in a large library. 
If you ask for a book in general it is very 
difficult to trace. Whereas if you ask for a 
particular book, the library staff can locate 
it very easily. How is it possible? In library 
the books are classified into various 
categories and sub categories. They 
are arranged on shelves accordingly. 
Therefore locating books become very 
easy. 

As on date one hundred and eighteen 
elements are known. It is difficult to identify 
each and every element individually and 
to know its property and uses. Therefore 
they have been classified on the basis 
of their similarities in properties. One of 



Henry Gwyn- 
Jeffreys Moseley, 
an English physicist 
(1887-1915), used 
X-rays to determine 
the atomic numbers 
of the elements. 



the important instincts of mankind is to be 
systematic. Scientists felt the necessity to 
group elements of similar characteristics 
together so that if the properties of one of 
them are known, those of the others could 
be guessed and related. 

When a large number of elements were 
discovered, several attempts were being 
made to arrange them on the basis of their 
properties, nature, character, valency, 
etc., (Real credit for preparing the periodic 

table goes to Mendeleev). 




12-1- MODERN PERIODIC LAW 

A large number of scientists made 
attempts to eleminate the drawbacks 
of Mendeleev's periodic table. In 1912, 
Moseley, an English physicist measured the 
frequencies of X-rays emitted by a metal, 
when the metal was bombarded with high 
speed electrons. He plotted square roots of 
the frequencies against atomic numbers. 
The plot obtained was a straight line. He 
found that the square root of the frequency 
of the prominent X-rays emitted by a metal 
was proportional to the atomic number and 
not to the atomic weight of the atom of that 
metal. 



MORE TO KNOW 



Atomic number is number of 
protons in the nucleus or number 
of electrons revolving around the 
nucleus in an atom. 



Moseley suggested that atomic 
number (Z) should be the basis of the 
classification of the element. Thus, he 
gave modern periodic law as follows: 

Modern periodic law states that "the 
physical and chemical properities of 
elements are the periodic function of 
their atomic numbers." 

Thus, according to the modern 
periodic law, if elements are arranged 
in the increasing order of their atomic 
numbers, the elements with similar 
properties are repeated after certain 
regular intervals. 




12-2- MODERN PERIODIC TABLE 

Based on the modern periodic law, a 
number of forms of periodic table have 
been proposed from time to time but 
general plan of the table remained the 
same as proposed by Mendeleev. The 
table which is most commonly used 
and which is based upon the electronic 
configuration of elements is called the 
long form of the periodic table. This is 
called the modern periodic table. 

12.2.1. Description of modern or 
long form of the periodic 
table 

Long form of the periodic table is a chart 
of elements in which the elements have 
been arranged in the increasing order of 
their atomic numbers. This table consists 
of horizontal rows called periods and 
vertical columns called groups. 



MORE TO KNOW 



The modern periodic table has also 
been divided into four blocks known 
as s,p,d and f blocks. 



12.2.3. Study of periods 

The horizontal rows are called 
periods. There are seven horizontal rows 
in the periodic table. 

• First period (Atomic number 1 and 2): 
This is the shortest period. It contains 
only two elements (hydrogen and 
helium). 

• Second period (Atomic number 3 to 1 0): 
This is a short period. It contains eight 
elements (lithium to neon). 

• Third period (Atomic number 11 to 18): 
This is also a short period. It contains 
eight elements (sodium to argon). 



12.2.2. Different portions of long form of periodic table 



Long form of 
periodic table 



1 



Left portion 


Group land 


G roup 2 


(Normal 


elements) 



M iddle portion 
G roups 3 to 12 



Right portion 

G roups 13 to 18 

(Normal 

elements) 



Transition elements 




Inner transition elements 



1 



iiiir^liliir 




(kept separately below the main body of periodic table) 



I PERIODIC CLASSIFICATION 




• Fourth period (Atomic number 1 9 to 36): 
This is a long period. It contains 
eighteen elements (potassium to 
krypton). This includes 8 normal 
elements and 10 transition elements. 

• Fifth period (Atomic number 37 to 54): 
This is also a long period. It contains 
18 elements (rubidium to xenon). This 
includes 8 normal elements and 10 
transition elements. 

• Sixth period (Atomic number 55 to 86): 
This is the longest period. It contains 
32 elements (ceasium to radon). 
This includes 8 normal elements, 
10 transition elements and 14 inner 
transition elements (lanthanides). 

• Seventh period (Atomic number 87 to 1 1 8): 
As like the sixth period, this period 
also can accomodate 32 elements. 
Till now only 26 elements have been 
authenticated by lUPAC. 

12.2.4. Study of groups 

• Vertical columns in the periodic table 
starting from top to bottom are called 
groups. There are 18 groups in the 
periodic table. 

• First group elements are called alkali 
metals. 

• Second group elements are called 
alkaline earth metals. 

• Groups three to twelve are called 
transition elements . 

• Group 1 , 2 and 1 3 - 1 8 are called normal 
elements or main group elements or 
representative elements . 



• Group 16 elements are called 
chalcogen family (except polonium). 

• Group 1 7 elements are called halogen 
family. 

• Group 18 elements are called noble 
gases or inert gases. 

• The lanthanides and actinides which 
form part of the group 3 are called 
inner transition elements. 

12,3- CHARACTERISTICS OF MOD- 
ERN PERIODIC TABLE 

12.3.1. Characteristics of Periods 

• In a period, the electrons are filled 
in the same valence shell of all 
elements. 

• As the electronic configuration 
changes along the period, the 
chemical properties of the elements 
also change. 

• Atomic size of the elements in a 
period decreases from left to the right. 

• In a period, the metallic character of 
the element decreases while their 
non-metallic character increases. 

12.3.2. Characteristics of Groups 

• The elements present in 2 and 18 
groups differ in atomic number by 
8,8,18,18,32. 

• The elements present in 13 - 17 
groups differ in atomic number by 
8,18,18,32. 

• The elements present in 4 - 12 
groups differ in atomic number by 
18,32,32. 



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Be 

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Mg 

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Ca 

Calcium 
40.078 

38 

Sr 

strontium 
87.62 


56 

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Barium 
137.327 


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Radium 
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I PERIODIC CLASSIFICATION 



• The elements present in a group 
have the same number of electrons 
in the valence shell of their atoms. 

• The elements present in a group 
have the same valency. 

• The elements present in a group 
have identical chemical properties. 

• The physical properties of the 
elements in group such as melting 
point, boiling point, density vary 
gradually. 

• Atomic radii of the elements present 
in a group increases downwards. 

12.3.3. Advantages of the Modern 
Periodic Table 

• The table is based on a more 
fundamental property ie., atomic 
number. 

• It correlates the position of 
the element with its electronic 
configuration more clearly. 

• The completion of each period is 
more logical. In a period as the 
atomic number increases, the 
energy shells are gradually filled 
up until an inert gas configuration 
is reached. 

• It is easy to remember and 
reproduce. 

• Each group is an independent 
group and the idea of sub-groups 
has been discarded. 

• One position for all isotopes of 
an element is justified, since the 
isotopes have the same atomic 
number. 

• The position of eighth group 



(in Mendeleev's table) is also 
justified in this table. All transition 
elements have been brought 
in the middle as the properties 
of transition elements are 
intermediate between left portion 
and right portion elements of the 
periodic table. 

• The table completely separates 
metals from non-metals. The non- 
metals are present in upper right 
corners of the periodic table. 

• The positions of certain elements 
which were earlier misfit (inter- 
changed) in the Mendeleev's 
periodic table are now justified 
because it is based on atomic 
number of the elements. 

• Justification has been offered for 
placing lanthanides and actinides 
at the bottom of the periodic 
table. 

12.3.4. Defects in the Modern 
Periodic Table 

• Position of hydrogen is not fixed 
till now. 

• Position of lanthanides and 
actinides has not been given inside 
the main body of periodic table. 

• It does not reflect the exact 
distribution of electrons of some 
of transition and inner transition 
elements. 




MORE TO KNOW 



The last element authenticated by lUPAC is Cn112 [Copernicium]. 
However, the nunnber of elennents discovered so far is 118. 



12A METALLURGY 




I PERIODIC CLASSIFICATION 



INTRODUCTION 

Metallurgy is as old as our civilization. 
Copper was the first metal to be used for 
making utensils, weapons and for other 
works. Metals play a significant role in our 
life. They constitute the mineral wealth of a 
country which is the measure of prosperity. 

Metals like titanium, chromium, 
manganese, zirconium etc. find their 
applications in the manufacture of defence 
equipments. These are called strategic 
metals. The metal uranium plays, a 
vital role in nuclear reactions releasing 
enormous energy called nuclear energy. 
Copper, silver and gold are called coinage 
metals as they are used in making coins, 
jewellery etc. 



MORE TO KNOW 



Purity of gold is expressed in carat. 
24 carat gold = pure gold. 

For making ornaments 22 carat gold 
is used which contains 22 parts of 
gold by weight and 2 parts of copper 
by weight. The percentage of purity is 
f X 100=91.6% (916 Make gold) 

From one gram of gold, nearly 2km 
of wire can be drawn. Its an amazing 
fact indeed! 




Vietnameses Craft Work in silver 




Aluminium foil 




Bangles 



MORE TO KNOW 



THE VITALITY OF METALS FOR THE TOTALITY OF LIFE 

Metals in minute amounts are essential for various biological 
purposes. Fe - a constituent of blood pigment (haemoglobin). 

Ca - a constituent of bone and teeth. Co - a constituent of vitamin B-12 

Mg - constituent of chlorophyll. 




METALS AROUND US 





12A TERMINOLOGIES IN 
METALLURGY 

12.4.1. Minerals: A mineral may be a 
single compound or complex mixture of 
various compounds of metals which are 
found in earth. 

12.4.2. Ores: The mineral from which a 
metal can be readily and economically 



extracted on a large scale is said to be a 
ore. 

For example, clay (AI2O3.2SiO2.2H2O) 
and bauxite (AI2O3.2H2O) are the two 
minerals of aluminium. But aluminium can 
be profitably extracted only from bauxite. 
Hence bauxite is an ore of aluminium 
and clay is its mineral. 




Gold 



Silver 



Aluminium 



I PERIODIC CLASSIFICATION 



12.4.3. Differences between miner- 
als and ores 

• Minerals contain a low percentage 
of metal while ores contain a large 
percentage of metal. 

• Metals cannot be extracted 
easily from mineral. On the other 
hand, ores can be used for the 
extraction of metals. 

• All minerals cannot be called as 
ores, but all ores are minerals. 

Mining: The process of extracting the 
ores from the earth crust is called mining. 

Metallurgy: Various steps involved in the 
extraction of metals from their ores as well 
as refining of crude metal are collectively 
known as metallurgy. 

Gangue or Matrix: The rocky impurity, 
associated with the ore is called gangue 
or matrix. 



Flux: It is a compound added to the ore 
to remove its impurities by fusion. eg. CaO 

Slag: It is the fusible product formed 
when flux reacts with gangue during the 
extraction of metals. 

Flux + Gangue -^ Slag 
Smelting: Smelting is the process of 
reducing the roasted oxide to metals in 
the molten condition. 

12.5. OCCURRENCE OF METALS 

Nearly 80 metallic elements are 
obtained from mineral deposits on or 
beneath the surface of the earth. Metals 
which have low chemical reactivity are 
found in free state, or in native state. 

Gold, silver and platinum are examples 
of metals that are partly found in a free 
state. Most of the other metals are found 
in a combined state in the form of their 
oxide ores, carbonate ores , halide ores, 
sulphide ores, sulphate ores and so on. 



Oxide Ores 


Carbonate Ores 


Halide Ores 


Sulphide Ores 


Bauxite 
(AI,0,.2H,0) 


Marble (CaCOj) 


Cryolite (NajAIFJ 


Galena (PbS) 


Cuprite (Cu^O) 


Magnesite (iVIgCOJ 


Fluorspar (CaF,) 


Iron pyrite (FeS,) 


Haematite (Fe^^) 


Siderite (FeCO,) 


Rock salt (NaCI) 


Zinc blende (ZnS) 



Flow Chart (Extraction of Metal from its ore) 



■ Gravity separation, Froth floatation, IVIagnetic 



separation. Leaching 
Concentrated ore 





Metals of high 
reactivity 

Electrolytic reduction 
refining 

f 

H Pure Metal B 



Metals of moderate 
reactivity j 

Calcination Roasting 
Reduction Refining 

♦ 

H Pure Metal B 



^^^etals of lov5^^ 
^^ reactivity ^J 

Roasting 
ure Metal ^B 




12-6- METALLURGY OF 

ALUMINIUM, COPPER AND 
IRON 

12.6.1. Metallurgy of aluminium 




ALUMINUM 
26,98 2J0 
660 2467 




Symbol : Al 
Colour : Silvery white 
Atomic number : 13 
Electronic 
configuration:2, 8, 3 
Valency : 3 
Atomic mass : 27 

Position in the periodic table: period=3, 
group=13(IIIA) 

Aluminium is the most abundant metal 
in the earth's crust. Since it is a reactive 
metal it occurs in the combined state. 
The important ores of aluminium are as 
follows: 



Name of the ore 


Formula 


Bauxite 


AIA-2H,0 


Cryolite 


Na3AIF3 


Corundum 


AIA 



The chief ore of aluminium is 
bauxite (AI2O3.2H2O). 

Extraction of aluminium from bauxite 
involves two stages: 1 



1. Conversion of Bauxite into 
Alumina by Baeyer's Process 

The conversion of Bauxite into Alumina 
involves the following steps: 

i. Bauxite ore is finely grounded and 
heated under pressure with concentrated 
caustic soda solution at 150°C to obtain 
sodium meta aluminate. 

AI2O3.2H2O + 2NaOH '^"^ 2NaAI02 + SH^O 

Sodium Meta 



Bauxite 



aluminate 



ii.On diluting sodium meta aluminate with 
water, aluminium hydroxide precipitate is 
obtained. 



NaAlO^ + 2H2O 



NaOH+AI(OH)3 

iii.The precipitate is filtered, washed, dried 
and ignited at 1000°C to get alumina. 



2AI(OH) 



3 ^^ AI2O3 + SHp 



2.Electrolytic reduction of Alumina 
by Hall's process 

Aluminium is produced by the electro- 
lytic reduction of fused alumina (AI2O3) in 
the electrolytic cell. 

Cathode : Iron tank lined with graphite 
Anode : A bunch of graphite rods 
suspended in molten electrolyte 
Electrolyte : Pure alumina + molten 
cryolite + fluorspar (fluorspar lowers the 
fusion temperature of electrolyte) 

Temperature : 900-950°C 

Voltage used : 5-6V 



The overall equation for aluminium extraction is 
2AI2O3 -^ 4AI + 30^ 



Aluminium deposits at cathode and 
oxygen gas is liberated at anode 



I PERIODIC CLASSIFICATION 



Graphitelined iron 
tank 




Refined 
aluminium 



Fig 12.6.3 Electrolytic refining of aluminium 

Properties of Aluminium 

Physical properties: 

It is a silvery white metal. 



very brightly forming its oxide and nitride. 

4AI + 3O2 -^ 2AI2O3 (Aluminium Oxide) 
2AI + N2 ^ 2AIN (Aluminium Nitride) 



i. It has low density and it is light 
ii.lt is malleable and ductile. 
V. It is a good conductor of heat and 
electricity. 



2. Reaction with water: Water has no 
reaction on aluminium due to the layer of 
oxide on it.When steam is passed over 
red hot aluminium, hydrogen is produced. 




2AI + SH^O 

steam 



^Al203 + 3H2T 

Aluminium 
Oxide 



3. Reaction with alkalis: It reacts with 
strong caustic alkalis forming aluminates. 



2AI + 2NaOH + 2Hp 



^ 2NaAI02 + SH^t 

Sodium meta 
aluminate 



Fig. 12.6.4 Electric conductivity of metal 
V. Melting point: 660°C 
vi.lt can be well polished to produce 
attractive shiny appearance. 

Chemical properties: 

1. Reaction with air: It is not affected by dry 

air.On heating at 800°C, aluminium burns 



4. Reaction with acids: With dilute and 
con. HCI it liberates H^ gas. 

2AI + 6HCI -^ 2AICI3 + SH^T 

Aluminium 
Chloride 

Aluminium liberates hydrogen on 
reaction with dilute sulphuric acid. Sulphur 
dioxide is liberated with hot concentrated 
sulphuric acid. 




2AI + SH^SO^ - 


-.AI,(SO,)3 + 3H,T 


Dilute 




2AI + 6H2SO4 - 


>Al2(S04)3 + 6H20+3S02t 


hot & cone. 


Aluminium 


Sulphuric acid 


Sulphate 



INDUSTRIAL VISIT 



MORE TO KNOW 



MORE TO KNOW 

Dilute or concentrated nitric acid 
does not attack aluminium. But it 
renders aluminium passive due to 
the formation of an oxide film on its 
surface. 



5. Reducing action : Aluminium is a 
powerful reducing agent. When a mixture of 
aluminium powder and iron oxide is ignited, 
the latter is reduced to metal. This process is 
known as aluminothermic process. 



Fe^Og + 2AI 



2Fe+Al203 



Uses of Aluminium 



1. Household 
utensils 



2. Electrical 
cable 
industry 

S.Aeroplanes 
and other 
industrial parts 



4.Thermite 
welding 



IJJiUtHI 



Aluminium 
metal 



Aluminium 
wires 



Duralumin 
(AI,Cu,Mg,Mn) 
Magnalium 
(AI.Mg) 



Al powder and 



It is light, cheap, cor- 
rosion resistant, and 
good conductor of 
heat. 

It is a good conductor 
of electricity. 



Its alloys are light, 
have high tensile 
strength and are 
corrosion resistant. 



Its powder is a strong 
reducing agent and 
reduces Fe.O. to iron. 





Make an industrial visit to 
the place where Thermite 
welding is actually 
done and record your 
observations on joining 
the gap between the 
broken pieces of rails. 



Fig 12.6.6 

12.6.2 IVIetallurgy of Copper 




Symbol : Cu 
Atomic mass : 63.55 
Atomic number : 29 
Electronic 

configuration : 2, 8, 18, 1 
Valency : 1 and 2 

Occurrence: It was named as cuprum 
by the Romans because they used to get 
it from the island of Cyprus. Copper is 
found in the native state as well as in the 
combined state. 



Ores of copper ^^^^^^^B 


'^i^PT _ 


i. Copper pyrite 

ii. Cuprite or ruby copper 

iii. Copper glance 


CuFeS^ 

Cup 

Cu^S 



Aircraft - An alloy of aluminium 



The chief ore of copper is copper 
pyrite. It yields nearly 76% of the world 
production of copper. 

Extraction from copper pyrites: 

Extraction of copper from copper pyrites 
involves the following steps. 



I PERIODIC CLASSIFICATION 



1. Crushing and concentration: The 

ore is crushed and then concentrated by 
froth-floatation process. 

2. Roasting: The concentrated ore is 
roasted in excess of air. During roasting, 

i. moisture and volatile impurities are 

removed. 

ii. copper pyrite is partly converted into 

sulphides of copper and iron. 



2CuFeS2 + O2 



Cu^S + 2FeS + SO2 



3. Smelting: The roasted ore is mixed with 
powdered coke and sand and is heated in 
a blast furnace to obtain matte and slag. 
(Matte = Cu^S + FeS) The slag is removed 
as a waste. 

4.Bessemerisation: The molten matte is 
transferred to Bessemer converter in order 
to obtain blister copper. Ferrous sulphide 
from matte is oxidised to ferrous oxide 
which is removed as slag using silica. 



2CU2S + 3O2 - 
2CU2O + Cu^S 



FeO+SiO. 



2CU2O + 2SO2 
-^ 6Cu + SO. 



^2 FeSiOgCiron silicate, slag) 
5. Refining: Blister copper contains 98% 
pure copper and 2% impurities and are 
purified by electrolytic refining. 

Electrolytic refining 

This method is used to get metal of high 
degree of purity. For electrolytic refining of 
copper, we use 

Cathode: A thin plate of pure copper 
metal. 

Anode: A block of impure copper metal. 

Electrolyte: Copper sulphate solution 
added with sulphuric acid. When electric 
current is passed through the electrolytic 



solution pure copper gets deposited at the 
cathode, impurities settled near the anode 
in the form of sludge called anode mud. 

Properties 

Physical properties: Copper is a reddish 
brown metal, with high lustre, high density 
and high melting point (1356°C). 
Chemical properties: 

i. Action of air and moisture: Copper 
gets covered with a green layer of basic 
copper carbonate in the presence of CO2 
and moisture. 

2Cu + O2 + CO2 + Hp -^ CuCOg.CuCOH)^ 
ii. Action of Heat: On heating at different 
temperatures in the presence of oxygen it 
forms two types of oxides CuO, CU2O. 

^^ ^ below 1370K^^ ^ , ^ 

2Cu + O2 ^ 2CuO (copper II oxide -black) 

above 1370K 

4Cu + O ^ 2Cu O (copper I oxide-red) 



iii. Action of Acids: a) with dil.HCI and 
dil-H^SG^ 

Dilute acids such as HCI and H^SO^ 
have no action on these metals in the ab- 
sence of air. Copper dissolves in these 
acids in the presence of air. 



2CUCI2 + 2Hp 



2Cu + 4HCI + O2 (air) 

2Cu + 2H2SO4 + O2 (air) -^ 2CUSO4 + 2H2O 

b) with dil.HNGg Copper reacts with dil. 
HNO3 with the liberation of Nitric Oxide 
gas. 

3Cu + 8HN03(dil) -^ SCuCNOg)^ + 2N0t + 4H2O 

c) with con.HNOg and con.H2S04 

Copper reacts with con. HNO3 and con. 
H^SG^ with the liberation of nitrogen 
dioxide and sulphur dioxide respectively. 

Cu + 4HNO3 -^ Cu(N03)2 + 2N02t + 2H2O 

(cone.) 




Cu + 2H2SO4 

(cone.) 



CuSO^ + SO4 + 2H,0 



iv. Action of chlorine: Chlorine reacts 
with copper, resulting in the formation of 
copper (II) chloride. 



Cu + CI2 -^ CuCI^ 

V. Action of all<alis: 

tacked by alkalis. 

Uses 



Copper is not at- 



• It is extensively used for making 
electric cables and other electric 
appliances. 

• It is used for making utensils, 
containers, calorimeters, coins. 

• It is used in electroplating. 

• It is alloyed with gold and silver for 
making coins and jewels. 

PROJECT 

Students may be asked to submit 
a project report on the important 
applications of copper in everyday 
life along with the samples. 

12-6-3 IVIETALLURGY OF IRON 




Symbol 


Fe 


Colour 


Greyish white 


Atomic mass 


55.9 


Atomic number 


: 26 


Valency 


2&3 


Electronic 




configuration : 


2. 8. 14. 2 



Occurrence: 

Iron is the second most abundant 
metal after aluminium. It occurs in nature 
as oxides, sulphides and carbonates. The 
ores of iron are given in the following table: 



Ores of iron 


Formula 


1. Haematite 


Fep3 


ii. Magnetite 


FesO, 


iii.lron pyrites 


FeS^ 



Extraction of Iron from haematite 
ore (Fe,03) 

1. Concentration by gravity separation 

The powdered ore is washed with 
stream of water. As a result, the lighter 
sand particles and other impurities are 
washed away and heavier ore particles 
settle down. 

2. Roasting and calcination 

The concentrated ore is strongly heated 
in a limited supply of air in a reverberatory 
furnace. As a result, moisture is driven 
out and sulphur, arsenic, phosphorus 
impurities are oxidised off. 

3. Smelting (in Blast furnace) 

The charge consisting of roasted ore, 
coke and limestone in the ratio 8 : 4 : 1 is 
smelted in a blast furnace by introducing 
it through the cup and cone arrangement 
at the top. There are three important 
regions in the furnance. 

i.The lower region(combustion zone)- 
temperature is at 1500° C. 

In this region, coke burns with oxygen 
to form CO2 when the charge comes in 
contact with the hot blast of air. 



I PERIODIC CLASSIFICATION 



1500°C 

C +0. > 



CO. + heat 



2 2 

It is an exothermic reaction since heat 
is liberated. 

ii.The middle region (fusion zone)-The 
temperature prevails at 1000°C.ln this 
region CO2 is reduced to CO. 



1000°C 

CO. + C ^ 



2CO 



Limestone decomposes to calcium 
oxide and CO2. 

A 



CaCO. 



CaO + CO. 



3 ^^^ ^^2 

These two reactions are endothermic 
due to the absorption of heat. Calcium 
oxide combines with silica to form calcium 
silicate slag. 



CaO + SiO. 



CaSiO. 



2 WV^W.Wg 

iii.The upper region (reduction zone)- 

temperature prevails at 400°C. In this 
region carbon monoxide reduces ferric 
oxide to form a fairly pure spongy iron. 



400°C 

^ 3Fe + SCO. 



Fe203 + SCO 

The molten iron is collected at the bot- 
tom of the furnace _after removing the slag. 

bell & hopper 



Pipe for 
hot air 
bla: 




2< — — Iron outlet 
Fig. 12.8.3 Blast furnace 



The iron thus formed is called pig 
iron. It is remelted and cast into different 
moulds. This iron is called cast iron. 



MORE TO KNOW 



CALCINATION AND ROASTING 
CALCINATION: It is a process in 
which ore is heated in the absence 
of air. As a result of calcination the 
carbonate ore is converted into its 
oxide. 

ROASTING: It is a process in which ore 
is heated in the presence of excess of 

air. As a result of roasting the sulphide 
ore is converted into its oxide. 



MORE TO KNOW 



Depending upon the carbon content 
iron is classified into 3 types. 

Pig iron with carbon content of 2- 4.5% 

Wrought iron with carbon content 

<0.25% 
Steel with carbon content of 0.25-2%. 



Physical properties 

It is a heavy metal of specific gravity 

7.9 

It is a lustrous metal and greyish white 

in colour. 

It has high tensility, malleability and 

ductility. 

It is a good conductor of heat and 

electricity. 

It can be magnetised. 




Chemical properties 

l.Reaction with air or oxygen: Only on 

heating in air, iron forms magnetic oxide. 

3Fe + 2O2 -^ Fep^ (black) 

2.Reaction with moist air: When iron is 
exposed to moist air, it forms a layer of 
brown hydrated ferric oxide on its surface. 
This compound is known as rust and the 
phenomenon of forming this rust is known 
as rusting. 

4Fe + 3O2 + SHp -^ 2Fe203.3H20(Rust) 

(Moisture) 

S.Reaction with steam: When steam is 
passed over red hot iron, magnetic oxide 
of iron is formed. 
3Fe + 4H20(steam) -^ ^ep^ + AH^t 

4.Reaction with chlorine: Iron combines 
with chlorine to form ferric chloride. 
2Fe + 3CI2 -^ 2FeCl3(ferric chloride) 

S.Reaction with acids: With dilute HCI 
and dilute H^SO^ it evolves H^ gas. 

Fe + 2HCI -^ FeCI^ + H^t 

Fe + H^SO^ -^ FeSO^ + H^t 

With cone. H^SO^ it forms ferric sulphate 

2Fe + 6H2SO4 -^ Fe2(S04)3 + SSO^ + GH^O 

With dilute HNO3 in cold condition it gives 

ferrous nitrate 

4Fe + IOHNO3 -^ 4Fe(N03)2 + NH4NO3 + 3Hp 

When iron is dipped in cone. HNO3 it 
becomes chemically inert or passive 

due to the formation of a layer of iron ox- 
ide {fep^) on its surface. 

Uses of iron 

i.Pig iron is used in making stoves, 

radiators, railings, man hole covers and 

drain pipes. 

ii. Steel is used in the construction of 



buildings, machinery, transmission and 
T.V towers and in making alloys. 
iii.Wrought iron is used in making 
springs, anchors and electromagnets. 

12-7 ALLOYS 

An alloy is a homogeneous mixture of 
two or more metals fused together. 
Alloys are solid solutions. Alloys can be 
considered as solid solutions in which the 
metal with high concentration is solvent 
and the metal with low concentration is 
solute. For example, brass is an alloy of 
zinc(solute) in copper(solvent). 

12.7.1 Methods of making alloys: 

l.By fusing the metals together. 
2. By compressing finely divided metals 
one over the other. 

Amalgam:An amalgam is an alloy of 
mercury with metals such as sodium, 
gold, silver, etc.. 



MORE TO KNOW 



DENTAL AMALGAMS 

It is an alloy of mercury with silver 
and tin metals. It is used in dental 
filling. 




I PERIODIC CLASSIFICATION 



12.7.2 Copper Alloys 



Name of the alloy 


Reason for alloying 


Uses 


i.Brass(Cu,Zn) 
ii.Bronze(Cu,Sn,Zn) 


Lusturous, easily 
cast,malleable, ductile, harder 
than Cu. 
Hard,brittle,takes up polish. 


Electrical fittings, medals, hard 
ware, decorative items. 

Statues, coins, bells, gongs. 



12.7.3 Aluminium Alloys 



Name of the alloy 


Reason for alloying 


Uses 


i.Duralumin(AI,Mg,Mn,Cu) 
ii.Magnalium(AI,Mg) 


Light,strong, resistant to corrosion, 
stronger than aluminium. 
Light,hard,tough, corrosion resistant. 


Aircraft.tools, pressure 

cookers 

Aircraft,scientific instrument 



12.7.4 Iron Alloys 



Name of the alloy 


Reason for alloying 


Uses 


i.Stainless steel (Fe,C,Ni,Cr) 
ii. Nickel steel (Fe,C,Ni) 


Lusturous, corrosion resistant,high 

tensile strength. 

Hard, corrosion resistant, elastic. 


Utensils, cutlery.automobile 

parts. 

Cables, aircraft parts, propeller. 



12-8 CORROSION 

Corrosion is defined as the slow and 
steady destruction of a metal by the 
environment. It results in the deterioration 
of the metal to fornn nnetal connpounds 
by means of chemical reactions with the 
environment. 

Water 
droplet 




IRON 



Rusting of iron 



MORE TO KNOW 



MECHANISM OF CORROSION 
Corrosion is a simple electro 
chemical reaction. 

When the surface of iron is in contact 

with moisture and other gases in the 

atmosphere an electrochemical 

reaction occurs. In this, impure iron 

surface acts as the cathode and pure 

iron acts as anode. H2CO3 formed 

from moisture and CO2 from air acts 
as electrolyte. 

The electrochemical reactions are 

as follows: 

Fe -^ Fe^' + 2e- 
O2 + 2Hp + 4e" -^ 40H" 
The Fe^^ ions are oxidised to Fe^^ ions. 
The Fe^^ ions combine with OH- ions 
to form Fe(OH)3.This becomes rust 
(Fe203.xH20) which is hydrated fer- 
ric oxide. 




ACTIVITY 9.1 







The conditions for rusting 

Take three test tubes provided with rubber corks and label them as A, B and C. 
Place few iron nails of same size in these tubes. Pour some water in test tube A, 
some boiled water along with turpentine oil in test tube B and anhydrous CaCl2 
in test tube C.Keep them under observation for few days. Notice the changes. 

The nails in A are rusted while the nails in B and C are unaffected. 

The rusting of nails in A is due to air and water. In B, the oily layer above water 
does not allow air to come in contact with nails. In C, the substance anhydrous 
CaCl2 has absorbed moisture completely. This activity shows that rusting of iron 
requires air and water. 



12.8.1 Methods of preventing 
corrosion 

Corrosion of metals is prevented by 
not allowing them to come in contact with 
moisture, CO2 and 02.This is achieved by 
the following methods: 

• By coating with paints: Paint coated metal 
surfaces keep out air and moisture. 

• By coating with oil and grease: Application 
of oil and grease on the surface of iron tools 
prevents them from moisture and air. 

• By alloying with other metals: Alloyed metal 
is more resistant to corrosion. 



Example: stainless steel. 
By the process of galvanization: This is a 
process of coating zinc on iron sheets by using 
electric current. In this zinc forms a protective 
layer of zinc carbonate on the surface of iron. 
This prevents corrosion. 
Electroplating: It is a method of coating one 
metal with another by passing electric current. 
Example: silver plating, nickel plating. This 
method not only lends protection but also 
enhances the metallic appearance. 
Sacrificial protection: Magnesium is more 
reactive than iron. When it is coated on the 
articles made of steel it sacrifices itself to 
protect the steel. 



I PERIODIC CLASSIFICATION 



PART A 

1 



EVALUATION 



In the modern periodic table 
periods and groups are given. 

Periods and groups indicate 

a) Rows and Columns b) Columns 
and rows 

2. Third period contains 8 elements, out 
of these elements how many elements 
are non-metals?. 

3. An element which is an essential 
constituent of all organic compounds 

belongs to group. 

(14^^ group/ 15^^ group) 

4. Ore is used for the extraction of 
metals profitably. Bauxite is used to 
extract aluminium, it can be termed as 
. (ore / mineral) 

5. Gold does not occur in the combined 
form. It does not react with air (or) 

water. It is in . (native state / 

combined state) 

PARTE 

6. Assertion: Greenish layer appears on 
copper vessels if left uncleaned. 

Reason: It is due to the formation of 
layer of basic copper carbonate 

Give your correct option. 

a) assertion and reason are correct and 
relevant to each other 

b) assertion is true but reason is not 
relevant to the assertion 

7. A process employed for the 
concentration of sulphide ore is 



(froth floation / gravity separation) 

8. Coating the surface of iron with other 
metal prevents it from rusting. If it is 
coated with thin layer of zinc it is called 

(galvanization / painting / 

cathodic protection) 

9. Any metal mixed with mercury is 
called amalgam. The amalgam 

used for dental filling Is . 

(Ag - Sn amalgam / Cu - Sn amalgam) 

10. Assertion In thermite welding, 
aluminium powder and Fe203 are 
used. Reason Aluminium powder is 
a strong reducing agent. Does the 
reason satisfy the assertion? 

PARTC 

11 . Can rusting of iron nail occur in distilled 
water. Justify your answer. 

12. Why cannot aluminium metal 
be obtained by the reduction of 
aluminium oxide with coke? 

13. Iron reacts with con. HCI and con. 
But it does not react with con. 

3. Suggest your answer with 
proper reason. 

14. To design the body of the aircraft 
aluminium alloys are used. Give your 
reason. 

15. X is a silvery white metal. X reacts with 
oxygen to form Y. The same compound 
is obtained from the metal on reaction 
with steam with the liberation of 
hydrogen gas. Identify X and Y. 



H,SO,. 
HNO, 



FURTHER REFERENCE: 

Books: Text Book of Inorganic chemistry - P.L. Soni S.CIiand Publishers 

Website: www.tutorvista.com. www.sciencebyjones.com 



Chapter 





41; 4^ 



i-V 






fr. -iAM. 



i!ilyt•V^.;^l 




CARBON AND ITS 
COMPOUNDS 



I CARBON AND ITS COMPOUNDS 




13. Carbon and its compounds 



Symbol 


C 


Atomic Number 


6 


Atomic IVIass 


12 


Valency 


4 



The electronic configration of carbon 
is K=2, L=4. It has four electrons in the 
valence shell and belongs to group IV A 
(group 14) of the periodic table. 




Fig. 13. 1 Electronic 
configuration of carbon 




Fig. 13.2 Compounds of carbon in different 
arrangement 



INTRODUCTION 

Without carbon, no living thing could 
survive. Human beings are made of 
carbon compounds. Carbon is a non 
metal. In nature, it occurs in its pure form 
as diamond and graphite. When fuels 
burn, the carbon in them reacts with 
oxygen to form carbon dioxide. 

Carbon compounds hold the key to 
plant and animal life on earth. Hence, 
carbon chemistry is called Living 
Chemistry. Carbon circulates through 
air, plants, animals and soil by means of 
complex reactions. This is called carbon 
cycle. 

13.1. COMPOUNDS OF 
CARBON 

In the beginning of 19th century scientists 
classified the compoundsof carbon into two 
types, based on their source of occurence: 
i) Inorganic compounds (obtained from 

non living matter) 
ii) Organic compounds (obtained from 
living matter, such as plant and 
animal sources) however the basis 
of classification was subjected to 
alteration after wohler synthesis. 






LIVING CHEMISTRY 

All living organisms are made of carbon atoms. This means that, carbon atoms 
form the building blocks for living organisms. These carbon atoms, in combination with 
other atoms decide life on earth. Hence carbon chemistry is also called as living 
chemistry. 





Fig. 13.3 Fig. 13A 

FRIEDRICH WOHLER 

A Greater of revolution in ORGANIC CHEMISTRY 



MORE TO KNOW 



ORGANIC CHEMISTRY: 

The word organic signifies life. The term organic chemistry 

was used by the Swedish chemist Berzelius. This refers 

to the chemistry of living things. However, the German 

chemist Wohler succeeded in creating an organic 

compound (urea) from an inorganic compound (ammonium 

cyanate) in his laboratory. This has dealt a severe blow to 

the vital force theory (a theory of life process). FRIEDRICH WOHLER 

A German Chemist 




I CARBON AND ITS COMPOUNDS 




13.2. MODERN DEFINITION OF 
ORGANIC CHEMISTRY 

Organic chemistry is defined as the 
branch of chemistry that deals with or- 
ganic compounds which are made up of 
the hydrocarbons and their derivatives. It 
gives a thorough insight into the nature of 
bonding, synthesis, characteristics and 
their usefulness in various fields. 



MORE TO KNOW 




A polished diamond 




The most precious diamond is a 
crystalline allotrope of carbon. KO- 
HINOOR DIAMOND is a 105 carat 
diamond (21.68g) It was seized by 
the EAST INDIA COMPANY and be- 
came the part of British Crown Jew- 
els. May it be an ordinary coal or the 
most precious Kohinoor diamond, it 
is an allotropic modification of 
carbon indeed! 



13.3. BONDING IN CARBON 
AND ITS COMPOUNDS 

The atomic number of carbon is 6 and 
its ground state electronic configuration 
is Is^ 2s2 2p2. Since it has four electrons 
in its outermost shell, its valency is four. 
To achieve noble gas configuration, 
carbon atom has to lose or gain four 
electrons to form C^^ and C^- ions. 

1 . It could gain four electrons forming C^" 
anion, but it would be difficult for the 
nucleus with six protons to hold on to 
ten electrons i.e.four extra electrons. 

2. It could lose four electrons to form C^^ 
cations, but it would require a large 
amount of energy to remove four 
electrons leaving behind the carbon 
cations with six protons in its nucleus 
holding on to just two electrons. 

Carbon overcomes this problem by 
sharing its valence electrons with other 
atoms of carbon or with atoms of other 
elements. This characteristic of carbon 
atom by virtue of which it forms four 
covalent bonds is generally referred as 
tetra valency of carbon. 

A molecule of methane (CH J is formed 
when four electrons of carbon are shared 
with four hydrogen atoms. 




H H 



Fig. 13.3 Structure of methane 
•• Represents shared pair of electrons 



13.4 ALLOPROPY 

Allotropy is defined as tine property by 
which an element can exist in more than 
one form that are physically different but 
chemically similar. 

Allotropes of carbon 

• Carbon exists in three allotropic forms. 
They are crystalline form (diamond 
and graphite), amorphous form 
(coke, charcoal) and fullerene. 

• In diamond each 
carbon atom is 
bonded to four 
other carbon 
atoms forming 
a rigid three 
dimensional 
structure, 
accounting for 
it's hardness 
and rigidity. 




Fig. 13 A 
Structure of diamond 



• In graphite each carbon atom is 
bonded to three other carbon atoms 
in the same plane giving hexagonal 
layers held together by weak vander 
Waals forces accounting for softness. 

• Graphite is a good conductor of 
electricity unlike other non-metals 
since it has free electrons in it. 



Fullerenes form 



another type of 
vander Waals force 




Fig. 13.5 Structure of graphite 
carbon allotropes. The first one was 
identified to contain 60 carbon atoms 
in the shape of a football. (C-60). 
Since this looks like the geodesic 



dome designed by the US architect 
Buck Minster Fuller, it is named as 
Buck Minster Fullerene. 




Fig. 13.6 Fullerene Fig. 13.7 Foot ball 

13.5 Physical nature of carbon and 
its compounds 

• Carbon has the ability to form 
covalent bonds with other atoms of 
carbon giving rise to large number 
of molecules through self linking 
property. This property is called 
catenation. Since the valency of 
carbon is four, it is capable of bonding 
with four other atoms of carbon. 

• Carbon combines with oxygen, 
hydrogen, nitrogen, sulphur, chlorine 
and many other elements to form 
various stable compounds. 

• The stability of carbon compounds is 
due to the small size of carbon which 
enables the nucleus to hold on to the 
shared pair of electrons strongly. 

• Carbon compounds show 
isomerism, the phenomenon by 
which two or more compounds to have 
same molecular formula but different 
structural formula with difference in 
properties, i.e the formula C^HgO 
represents two different compounds 
namely ethyl alcohol (C^H^GH) and 
dimethyl ether (CH3OCH3). 

• Carbon compounds have low melting 
and boiling points because of their 
covalent nature. 



I CARBON AND ITS COMPOUNDS 




• The reactions shown by carbon 
compounds involve breaking of old 
bonds in the reacting molecules and 
the formation of new bonds in the 
product molecules. 

• Carbon compounds are easily 
combustible. 

13.6 CHEMICAL PROPERTIES 

• Carbon and its compounds burn in 
oxygen to give carbon dioxide along 
with heat and light. 

e.g., 

C + O2 ^ CO2+ heat + light 

CH^ + 2O2 -^ CO2 + 2Hp + heat + light 
C^H^H + 2O2 -^ 2CO2 + 3Hp + heat + light 

• Carbon compounds can be easily 
oxidized using suitable oxidizing agent 
(Alkaline potassium permanganate) to 
form carboxylic acids. 

• Unsaturated carbon compounds 
undergo addition reactions with 
hydrogen in the presence of palladium 
or nickel catalyst. 

e.g., 

Addition of hydrogen 



CH2 = CH2 
Ethene 



Ni-catalyst 



.CH3-CH3 
Ethane 



• Carbon compounds undergo 
substitution reactions in the presence 
of either sunlight or any other 
reagents. E.g methane undergoes 
substitution reaction to form different 
types of products. 

• Carbon compounds such as alcohols 
react with sodium to liberate 
hydrogen gas. 

e.g: 2CH3CKOH + 2Na^2CH3CKONa + K 



13.7 HOMOLOGOUS SERIES 

A homologous series is a group or a 
class of organic compounds having similar 
structure and similar chemical properties 
in which the successive compounds differ 
by a CH2 group. 

13.7.1 Characteristics of 
homologous series 

• Each member of the series differs from 
the preceeding or succeeding member 
by a common difference of CH^ 
and by a molecular mass of 14 amu 
(amu = atomic mass unit). 

• All members of homologous series 
contain same elements and the same 
functional groups. 

• All members of homologous series 
have same general molecular formula. 

eg Alkane = C^H,^,, 

Alkene = C H, 

n 2n 

Alkyne = C„H,„., 

• The members in homologous series 
show a regular gradation in their 
physical properties with respect to 
increase in molecular mass. 

• The chemical properties of the 
members of the homologous series 
are similar. 

• All members of homologous series 
can be prepared by using same 
general method. 






13-8 IMPORTANCE OF 

HOMOLOGOUS SERIES 

1 . It helps to predict the properties of the 
members of the series that are yet to 
be prepared. 

2. Knowledge of homologous series gives 
a systematic study of the members. 

3. The nature of any member of the fam- 
ily can be ascertained if the properties 
of the first member are known. 

13-9 HYDROCARBONS 

The simplest organic compounds 
containing only carbon and hydrogen 
are called Hydrocarbons. These are 
regarded as the parent organic com- 
pounds and all other compounds are 
considered to be derived from them by 
the replacement of one or more hydrogen 
atoms by other atoms or groups of atoms. 

Hydrocarbons are classified into two 
types: saturated and unsaturated hydro- 
carbons. 

13.9.1 Saturated hydrocarbons - 
Alkanes 

General formula = C H, ^^Suffix : ane 

n 2n+2 

These are the organic compounds 
which contain carbon - carbon single 
bond. These were earlier named as 

paraffins(Latin : meaning little affinity) 
due to their least chemical reactivity. 
According to lUPAC system, these are 
named as alkanes (ane is suffix with 
root word). 



Formula 


Common 


lUPAC 




name 


name 




CH, 


Methane 


Methane 


CH3CH3 


Ethane 


Ethane 


CH3CH,CH3 


Propane 


Propane 


CH3CH2CH2CH3 


n-Butane 


Butane 



13.9.2 Unsaturated hydrocarbons 

These are hydrocarbons which contain 



carbon to carbon double bonds 



f I 

or carbon to carbon triple bonds -C=C- 

in their molecules.These are further 

classified into two types: alkenes and 

alkynes. 

\)Alkenes: General formula: CH^^Suffix: ene 

The hydrocarbons containing atleast one 
carbon to carbon double bond are called 
a//cenes.They have the general formula 
C^H^^ .These were previously called 
olefins (Greek : defiant - oil forming) 
because the lower gaseous members of 
the family form oily products when treated 
with chlorine. 

In lUPAC system, the name of alkene 
is derived by replacing suffix ane of the 
correspding alkane by ene. For example, 



CH3 - CH3 

ethane 



H2C=CH2 
ethene 




Fig. 13.8 Bromine Test 



(Left) No change in colour - saturated, 
(Right) Decolouration occurs - unsaturated 



I CARBON AND ITS COMPOUNDS 




In higher alkenes, the position of the double bond, can be indicated by assigning 
numbers 1, 2, 3, 4, to the carbon atoms present in the molecule. 



Alkene 


Common name 


lUPAC name 


CH^ = CH^ 


Ethylene 


Ethene 


CH3CH = CH^ 


Propylene 


Propene 


CH3CH2-CH=CH2 


a-Butylene 


But-1-ene 


CH3CH = CHCH3 


P-Butylene 


But-2-ene 



ii) Alkynes: General formula: C^H2^.2 Suffix : yne 

The hydrocarbons containing carbon to carbon triple bond are called alkynes. 
Alkynes are named in the same way as alkenes i.e., by replacing suffix ane of alkane 
by yne. In higher members, the position of triple bond is indicated by giving numbers 
1, 2, 3, 4, ....to the carbon atom in the molecule. 



Alkyne 


Common name 


lUPAC name 


HCECH 
H3C-CECH 
H3C - C EC - CH3 
H3C - CH^ -C E CH 


Acetylene 
Methyl acetylene 
Dimethyl acetylene 
Ethyl acetylene 


Ethyne 
Propyne 
But-2-yne 
But-1-yne 



13-10- FUNCTIONAL GROUP 

Functional group maybe defined as an atom or group of atoms or reactive 
part which is responsible for the characteristic properties of the compounds. 

The chemical properties of organic compounds are determined by the functional 
groups while their physical properties are determined by the remaining part of the 
molecule. 



Example: -OH => Alcohol 
-OHO => Aldehyde 



/C=0 => Ketone 

- GOGH => Garboxylic acid 



13.10.1. Classification of organic compounds based on functional group 

1. Alcohols 

Alcohols are carbon compounds containing -OH group attached to alkyl 
group. The general formula of alcohol is R-OH where 'R' is an alkyl group 
and -OH is the functional group. The lUPAG name of alcohol is derived by 
replacing -e, in the word alkane, by the suffix -ol. Hence we get the name 
alkanol. 



Molecular formula 


Common name 


lUPAC name 


CH3OH 


Methyl alcohol 


Methanol 


CH3-CH2-OH 


Ethyl alcohol 


Ethanol 


CH3- CH^-CH^-OH 


n-Propyl alcohol 


1-Propanol 


CH3-CH-CH3 

1 


Isopropyl alcohol 


2-Propanol 


OH 


or secondary propyl alcohol 




CH3- CH^-CH^-CH^-OH 


n-Butyl alcohol 


1-Butanol 


CH3-CH-CH2-OH 

1 


Isobutyl alcohol 


2-Methyl-l-propanol 


CH3 







2. Aldehydes 

Aldehydes are carbon compounds containing -CHO group attached to alkyl 
group or hydrogen atom. The general formula of aldehydes is R - CHO where 
'R' is an alkyl group or hydrogen atom and - CHO is the functional group. 
The lUPAC name of aldehyde is derived by replacing -e, in the word alkane, 
by the suffix -al. Hence we get the name "alkanal". 



Molecular formula 


Common name 


lUPAC name 


HCHO 


Formaldehyde 


Methanal 


CH3- CHO 


Acetaldehyde 


Ethanal 


CH3- CH^- CHO 


Propionaldehyde 


Propanal 


CH3- CH^-CH^- CHO 


Butyraldehyde 


Butanal 



3. Ketones 

Ketones are carbon compounds containing carbonyl - CO - group attached 
to two alkyl groups. The general formula of ketone is R-CO-R' where R and 
R' are alkyl groups and - CO - is the functional group. The lUPAC name 
of ketone is derived by replacing -e, in the word alkane, by the suffix -one. 
Hence we get the name "alkanone". 



I CARBON AND ITS COMPOUNDS 




Molecular formula 


Common name 


lUPAC name 


CH3COCH3 

CH3COCH2CH3 

CH3CH2COCH2CH3 


Dimethyl ketone (Acetone) 
Ethyl methyl ketone 
Diethyl ketone 


Propanone 

Butanone 
3-Pentanone 



4. Carboxylic Acids 

Carboxylic acids are carbon compounds containing -COOH group attached 
to a hydrogen atom or alkyl group. The general formula of acid is R-COOH 
where 'R' is a hydrogen atom or alkyl group and -COOH is the functional 
group. The lUPAC name of acid is derived by replacing - e, in the word alkane, by 
the suffix -oic acid. Hence we get the name "alkanoic acid". 



Molecular formula 


Common name 


lUPAC name 


HCOOH 


Formic acid 


Methanoic acid 


CH3-COOH 


Acetic acid 


Ethanoic acid 


CH3- CH^-COOH 


Propionic acid 


Propanoic acid 


CH3- CH^-CH^-COOH 


n-Butyric acid 


Butanoic acid 



SOME IMPORTANT ORGANIC COMPOUNDS 

Almost all the compounds are useful to us in a number of ways. Most of the fuels, 
medicines, paints, explosives, synthetic polymers, perfumes and detergents are 
basically organic compounds. In fact, organic chemistry has made our life colourful 
and also comfortable. Two commercially important compounds, ethanol and ethanoic 
acid are briefly discussed here. 

13-11 ETHANOL (C^H^OH) 

Ethanol or ethyl alcohol or simply alcohol is one of the most important members 
of the family of alcohols. 






(1) Manufacture of ethanol from molasses 

Molasses is a dark coloured syrupy liquid left after the crystallization of sugar from 
the concentrated sugar cane juice. Molasses still contain about 30% of sucrose which 
can not be separated by crystallization. It is converted into ethanol by the following 
steps: 

(i) Dilution 

Molasses is first diluted with water to bring down the concentration of sugar to 
about 8 to 10 percent. 

(ii) Addition of ammonium salts 

Molasses usually contains enough nitrogenous matter to act as food for yeast 
during fermentation. If the nitrogen content of the molasses is poor, it may be 
fortified by the addition of ammonium sulphate or ammonium phosphate. 

(iii) Addition of yeast 

The solution from step (ii) is collected in large 'fermentation tanks' and yeast is 
added to it. The mixture is kept at about 303K for a few days. During this period, 
the enzymes invertase and zymase present in yeast, bring about the conversion 
of sucrose into ethanol. 

C,,H,,0,, + H,0 ^^^^21^^^ C^H^A + C,H,A 

Sucrose Glucose Fructose 

CgH^Pg ^^^^^^ > 2C2H3OH + 2CO2 T 

Glucose or Fructose Ethanol 

The fermented liquid is technically called wash. 

(iv) Distillation of wash 

The fermented liquid containing 15 to 18 percent alcohol and the rest of the water, 
is now subjected to fractional distillation. The main fraction drawn, is an aqueous 
solution of ethanol which contains 95.5% of ethanol and 4.5% of water. This is called 
rectified spirit. This mixture is then heated under reflux over quicklime for about 5 to 
6 hours and then allowed to stand for 12 hours. On distillation of this mixture, pure 
alcohol (100%) is obtained. This is called absolute alcohol. 



I CARBON AND ITS COMPOUNDS 




MORE TO KNOW 



FERMENTATION 



The slow chemical change taking place in an organic compound by the 
action of enzymes leading to the formation of smaller molecules is called 
fermentation. 

2- Physical properties 

(i) Ethanol is a clear liquid with burning taste. 

(ii) Its boiling point is 351 K which is higher than corresponding alkane. 
(iii) It is completely miscible with water in all proportions. 

3- Chemical properties 

(i) Dehydration 

(a) Intra molecular dehydration : Ethanol, when heated with excess cone. H^SO^ at 
443 K undergoes intra molecular dehydration (i.e. removal of water within a 
molecule of ethanol). 

Conc.H.SO^ 

CHXH^OH —k CH =CH +H,0 

2 2 443K 

Ethanol Ethene 



(b) Inter moleculardehydration:When excess of alcohol is heatedwithconc.H^SO^ 
at 41 3K two molecules condense by losing a molecule of water to form ether 
(i.e. removal of water from two molecules of ethanol). 

Conc.H.SO^ 
C,H - OH + HO- C,H, ^^' ' > C,H -0-C,H +H,0 

2 5 2 5 413K 2 5 2 5 2 

Diethyl ether 

(ii) Reaction with sodium : Ethanol reacts with sodium metal to form sodium 

ethoxide and hydrogen gas. 

► 2C^\-\pMa + H^] 

sodium ethoxide 



2C2H3OH + 2Na 



(iii) Oxidation : Ethanol is oxidized to ethanoic acid with alkaline KMnO or acidified 



K,Cr,0, 



CH3CH2OH Oxidation ^ c|-|^cqq|-| +y^p 

Ethanoic acid 






During this reaction, orange colour of K^Cr^O^ changes to green. Therefore, this 
reaction can be used for the identification of alcohols. 

(iv) Esterificaiton : Ethanol reacts with ethanoic acid in the presence of conc.H^SO^ 

(catalyst) to form ethyl ethanoate and water. The compound formed by the reaction 

of an alcohol with carboxylic acid is known as ester (fruity smelling compound) and 

the reaction is called esterification. 

conc.H.SO, 

C.H OH + CH XOOH —^ CH nOOC.H + HO 

Ethanol Ethanoic acid Ethyl ethanoate 

(v) Dehydrogenation : When the vapour of ethanol is passed over reduced copper 
catalyst at 573 K, it is dehydrogenated to acetaldehyde. 

CH3CHPH ,;;k ► CH3CH0+H, 

Ethanol Acetadehyde 

4. Uses 

Ethanol is used 

1. As an anti-freeze in automobile radiators. 

2. As a preservative for biological specimen. 

3. As an antiseptic to sterilize wounds in hospitals. 

4. As a solvent for drugs, oils, fats, perfumes, dyes, etc. 

5. In the preparation of methylated spirit (mixture of 95% of ethanol and 5% of methanol), 
rectified spirit (mixture of 95.5% of ethanol and 4.5% of water), power alcohol 

(mixture of petrol and ethanol) and denatured sprit (ethanol mixed with pyridine). 

6. In cough and digestive syrups. 

Evil effects of consuming alcohol 

• If ethanol is consunned, it tends to slow down nnetabolisnn of our body 
and depresses the central nervous system. 

• It causes mental depression and emotional disorder. 

• It affects our health by causing ulcer, high blood pressure, cancer, 
brain and liver damage. 

• Nearly 40% accidents are due to drunken drive. 



I CARBON AND ITS COMPOUNDS 




• Unlike ethanol, intake of methanol in very small quantities can cause death. 

• Methanol is oxidized to methanal (formaldehyde) in the liver and methanal 
reacts rapidly with the components of cells. 

• Methanal causes the protoplasm to get coagulated, in the same way an egg 
is coagulated by cooking. Methanol also affects the optic nerve, causing 
blindness. 



13.12. ETHANOIC ACID (CH3COOH) 

Ethanoic acid is most commonly known as acetic acid and belongs to a group 
of acids called carboxylic acids. Acetic acid is present in many fruits and sour taste of 
fruits is because of this acid. 

1. Preparation of Ethanoic acid 

Ethanol on oxidation in the presence of alkaline potassium permanganate or acidi- 
fied potassium dichromate gives ethanoic acid. 

Oxidation 
CH3CH2OH ►CH3COOH+H2O 

Ethanol Ethanoic acid 

2. Physical properties 

(i) Ethanoic acid is a colourless liquid and has a sour taste. 

(ii) It is miscible with water in all proportions. 

(iii) Boiling point (391 K) is higher than corresponding alcohols, aldehydes and 

ketones. 

(iv) On cooling, pure ethanoic acid is frozen to form ice like flakes. They look like 
glaciers, so it is called glacial acetic acid. 

3. Chemical properties 

(1) Ethanoic acid is a weak acid but it turns blue litmus to red. 
(ii) Reaction with metal 

Ethanoic acid reacts with metals like Na, K, Zn, etc to form metal ethanoate and hydrogen gas. 



2CH3COOH + Zn ► (CH3COO)2Zn + H^ t 

2CH3COOH + 2Na ► 2CH3COONa + H^ t 

(iii) Reaction with carbonates and bicarbonates. 

Etiianoic acid reacts witii carbonates and bicarbonates and produces brisk 
effervescence due to tine evolution of carbon dioxide. 

2CH3COOH + Na2C03 ► 2CH3COONa + CO^ t + H^O 

CH3COOH + NaHC03 ► CH3C00Na + CO^ t + \-\p 

(iv) Reaction with base 

Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water. 

CH3COOH + NaOH ► CH3C00Na + Hp 

(v) Decarboxylation (Removal of CO^) 

When sodium salt of ethanoic acid is heated with soda lime (Solid mixure of 3 parts 

of NaOH and 1 part of CaO) methane gas is formed. 

CH3C00Na ^^^^^^^^ ► CHJ + Na2C03 
4- USES 

Ethanoic acid is used 

1 . For making vinegar which is used as a preservative in food and fruit juices. 

2. As a laboratory reagent. 

3. For coagulating rubber from latex. 

4. In the preparation of dyes, perfumes and medicine. 

EVALUATION 
PART A 

1. Assertion: Chemical bonds in organic compounds are covalent in nature. 
Reason: Covalent bond isformed by the sharing of electrons in the bonding atoms. 
Does the reason satisfy the given assertion? 

2. Assertion: Diamond is the hardest crystalline form of carbon 
Reason: Carbon atoms in diamond are tetrahedral in nature. 

Verify the suitability of reason to the given Assertion mentioned above. 



I CARBON AND ITS COMPOUNDS 




3. Assertion: Due to catenation a large number of carbon compounds are formed. 
Reason: Carbon compounds show the property of allotropy. 

Is the reason holding good for the given Assertion. 

4. Buckminster Fullerene is the allotropic form of (Nitrogen / Carbon / Sulphur) 

5. Eventhough it is a non metal, graphite conducts electricity. It is due to the 
presence of (free electrons / bonded electrons) 

6. Formula of methane is CH^ and its succeeding member ethane is expressed 
as C^Hg. The common difference of succession between them is (CH^ / C^ H^) 

7. lUPAC name of first member of alkyne is (ethene / ethyne) 

8. Out of ketonic and aldehydic group which is the terminal functional group? 

9. Acetic acid is heated with a solid X kept in a test tube. A colourless and 
odourless gas (Y) is evolved. The gas turns lime water milky when passed 
through it. Identify X and Y. 

10. Assertion: Denaturation of ethyl alcohol makes it unfit for drinking purposes. 
Reason: Denaturation of ethyl alcohol is carried out by methyl alcohol. 
Check whether the reason is correct for assertion. 

PARTB 

11 . Write down the possible isomers and give their lUPAC names using the 
formula C^H^q. 

12. Diamond is the hardest allotrope of Carbon. Give reason for its hardness. 

13. An organic compound (A) is widely used as a preservatives in pickles and has a 
molecular formula C2H^02. This compound reacts with ethanol to form a sweet 
smelling compound (B). 

(i) Identify the compound A and B. 

(ii) Name the process and write corresponding chemical equation. 

14. An organic compound (A) of molecular formula C2HgO on oxidation with alkaline 
KMnO^ solution gives an acid (B) with the same number of carbon atoms. 
Compound A is used as an antiseptic to sterilize wounds in hospitals. Identify A 
and B. Write the chemical equation involved in the formation of B from A. 






PARTC 

15. Fill in the blanks using suitable formula in the given table 



No. 


Alkane 


Alkene 


Alkyne 


1. 


C, H^ ethane 


ethene 


C2 H2 ethyne 


2. 


Propane 


C3 HgPropene 


propyne 


3. 


C^ H^Q Butane 


Butene 


Butyne 



16. Homologous series predict the properties of the members of hydrocarbon. 

Justify this statement through its characteristics. 

17. Write the common name and lUPAC name of the following. 

a) CH3CH2CHO b) CH3COCH3 

C) CH3 - CH - CH3 d) CH3 COOH 

OH 
e) HCHO 

FURTHER REFERENCE 

Books: l.Oraganic chemistry - B.S. Bahl & Arun Bahl S.Chand Publishers 

2. Organic chemistry - RT. Morrision & R.N. Boyd - Practice Hall 
Publishers. 

Website: www.tutorvista.com, www.topperlearning.com 



Chapter 






MEASURING 
r INSTRUMENTS 




14. Measuring Instruments 



Physics is the most basic science, which 
deals with the study of nature and natural 
phenomena. It is a quantitative science. 
Therefore physicists measure things. 
The ultimate test of any physical quantity 
is its agreement with observations and 
measurement of physical phenomena. 
One of the major contributions of physics 
to other sciences and society are the many 
measuring instruments and techniques 
that physics has developed. One such 
instrument is screw gauge. 



14.1 SCREW GAUGE 

Screw Gauge is an instrument to 
measure the dimensions of very small 
objects upto 0.001 cm. 

The Screw Gauge consists of 'U' 
shaped metal frame Fig. 14.1. 

A hollow cylinder is attached to one 
end of the frame. 



Grooves are cut on the inner surface 
of the cylinder through which a screw 
passes through. 

On the cylinder parallel to the axis of the 
screw a scale is graduated in millimeter 
called Pitch Scale. 

One end of the screw is attached to a 
sleeve. 

The head of the sleeve is divided into 
100 divisions called as the Head Scale. 

The other end of the screw has a plane 
surface (s^). 

A stud (S2) is attached to the other 
end of the frame, just opposite to the tip 
of the screw. 

The screw head is provided with a 
ratchat arrangement (safety device) to 
prevent the user from exerting undue 
pressure. 



82 



I. 



Hallow Cylindrical tube 



Milled Head (H) 



Safety device (D) 
(Ratchat) 




U-Shaped Frame 




pitch scale 

Head Scale 
Index line 



Fig 14.1 



MEASURING INSTRUMENTS 




Principle of the Screw Gauge 

Screw Gauge works under the principle 
of the screw. When a screw is rotated in 
a nut, the distance moved by the tip of 
the screw is directly proportional to the 
number of rotations. 



Pitch of the screw 

Pitch of the screw is the distance 
between two screw threads. It is also 
equal to the distance travelled by the tip 
of the screw for one complete rotation of 
the head. 



Distance travelled on the pitch scale 



Pitch = 



No. of rotations 



Least Count of a Screw Gauge 

The distance moved by the tip of the 
screw for a rotation of one division on the 
head scale is called the least count of the 
Screw Gauge. 




Zero Error of a Screw Gauge 

The plane surface of the screw and 
the opposite plane stud on the frame are 
brought into contact. 

No Zero Error 









5 

95 1 
















. If the zero of the head scale coincides 
with the pitch scale axis, there is no zero 
error.Fig. 14.2 

Positive Zero Error 



"Z 



Fig. 14.3 



10 



If the zero of the head scale lies 
below the pitch scale axis, the zero error 
is positive. If the n^^ division of the head 
scale coincides with pitch scale axis the 
zero error is positive. Fig. 14. 3 

Z.E = + (nxL.C), 

Then the Zero Correction 

Z.C = -(nxL.C) 

Negative Zero Error 










95 
90 

1 




1 













Fig. 14.2 



Fig 14.4 

If the Zero of the head scale lies above 
the pitch scale axis, the zero error is 
negative. If the n*^ division coincides with 
the pitch scale axis, the zero error is 
negative. Fig. 14.4 

Z.E = -(100-n)xL.C, 

Then the Zero Correction 

Z.C = + (100-n)xL.C 




To measure the diameter of a 
thin wire using Screw Gauge 

• Determine the Pitch, the Least 
count and the Zero Error of the 
Screw Gauge. 

• Place the wire between two studs. 

• Rotate the head until the wire is 
held firmly but not tightly, with 
the help of ratchat. 

• Note the reading on the 
pitch scale crossed by 
the head scale (PSR) and 
the head scale reading coincides 
with the head scale axis (H.S.C). 

• The diameter of the wire is given 
by P.S.R + (H.S.Cx L.C) ±Z.C 

• Repeat the experiment for 
different portions of the wire. 

• Tabulate the readings. 

• The average of the last column 
reading gives the diameter of 
the wire. 



S.No 


P.S.R 
mm 


H.S.C 


H.S.Cx 
L.C mm 


Total Reading 

P.S.R + 

(H.S.CxLC) 

fZ.C mm 


1 










2 










3 











Nowadays we have digital Screw 
Gauge to take the reading at once. 



14.2 Measuring long distances 

For measuring long distances such 
as distance of the moon or a planet 
from the earth, special methods are 
adopted. Radio echo method, laser pulse 
method and parallax method are used to 
determine very long distances. In order 
to measure such very long distances the 
units astronomical distance and light year 
are used. 

Astronomical distance 

Astronomical distance is the mean 
distance of the centre of the sun from the 
centre of the earth. 

1 Astronomical unit (AU) 
= 1.496 X 10^1 m 

Light year 

Light year is the distance travelled by 
light in one year in vacuum. 

Distance traveled by light in one year 
in vacuum = Velocity of light x I year (in 
seconds) 

= 3 X 10^ X 365.25 x 24 x 60 x 60 

= 9.467 X 10^^ m 

Therefore , 1 light year = 9.467 x 10^^ m 

EVALUATION 

PART A 

1. Screw gauge is an instrument to 
measure the dimensions of very small 
objects upto 

(0.1 cm., 0.01 cm., 0.1 mm., 0.01 mm) 

2. In a screw gauge zero of the head scale 



MEASURING INSTRUMENTS 




lies below the pitch scale axis, the zero 
error is 

(positive, negative, nil) 

3. Screw gauge is used to measure the 
diameter of 

( crow bar, thin wire, cricket ball ) 

4. One light year is equal to 



( 365.25 X 24 X 60 X 60 X 3 X 10^ m , 
1 X 24 X 60 X 60 X 3 X 0^ m , 
360 X 24 X 60 X 60 X 3 X 10^ m ) 

5. One astronomical unit is the distace 
between the centre of the earth and 



(centre of the Moon, centre of the Sun, 
centre of the Mars) 

PART B 

1. Correct the mistakes if any, in the 
following statements. 

Astronomical distance is the mean 
distance of the surface of the sun from 
the surface of the earth. 

Light year is the distance travelled by 
light in one year in vacuum at a speed of 
3x10^ m. per minute 



2. Match the items in group A with the 
items in group B 



Group A 


Group - B 


Small dimensions 


Kilo meter 


Large dimensions 


Screw gauge 


Long distances 


Scale 


Small distances 


Light year 




Altimeter 

1 



3. Fill in the blanks: Special methods 
adopted to determine very large 

distances are and 

(Laser pulse method, 



Light year method, Radio echo method) 

4. Least count of a screw gauge is an 
important concept related to screw 
gauge. What do you mean by the term 
least count of a screw gauge. 

5. Label the following parts of the screw 
gauge in the given screw gauge 
diagram. 

1. Head scale 2. Pitch scale 



3. Axis 



4. Ratchat 




^^^Ijlia 



FURTHER REFERENCE : 

Books: 1. Complete physics for IGCSE - Oxford publications. 

2. Practical physics - Jerry. D. Wilson - Saunders college publishing 
Webste: www.complore.com 
www.physlink.com 



Chapter 



m 





LAWS OF MOTION AND 
GRAVITATION 



LAWS OF MOTION AND GRAVITATION 



bJ 



15. Laws Of motion and 

gravitation 



In our everyday life, we observe that 
some effort is required to put a stationary 
object into motion or to stop a moving 
object. Normally we have to push or pull or 
hit an object to change its state of motion. 

The concept of force is based on this 
push, pull or hit. No one has seen, tasted, 
or felt force. However, we always see or 
feel the effect of a force. It can only be 
explained by describing what happens 
when a force is applied to an object. Push, 
pull or hit may bring objects into motion, 
because we make a force to act on them. 
Therefore, force is one which changes 
or tends to change the state of rest or 
of uniform motion of a body. Force is a 
vector quantity. Its SI unit is newton. 

15.1. BALANCED AND 

IMBALANCED FORCES 

Fig. 15.1 shows a wooden block on a 
horizontal table. Two strings X and Y are 
tied to the two opposite faces of the block 
as shown. 

If we apply a force by pulling the string 
X, the block begins to move to the right. 



^ 



Fig. 15.1 

Similarly, if we pull the string Y, the block 
moves to the left. But, if the block is pulled 
from both the sides with equal forces the 
block will not move and remains stationary. 
Forces acting on an object which do not 
change the state of rest or of uniform 
motion of it are called balanced forces. 
Now let us consider a situation in which 
two opposite forces of different magnitudes 
act on the block. The block moves in the 
direction of the greater force. The resultant 
of two forces acts on an object and brings 
it in motion. These opposite forces are 
called imbalanced forces. 

The following illustration clearly explains 
the concept of balanced and imbalanced 
forces. Some children are trying to push a 
box on a rough floor. 






(a) 






f^^^^^^m 


; 




^'^ 


t 




/ 




(c) 
F/g. 15.2 

If one boy pushes the box with a smaller 
force, the box does not move because of 
friction acting in a direction opposite to the 
push [Fig. 15.2(a)] This friction force arises 
between two surfaces in contact. In this 
case, between the bottom of the box and the 
floor rough surface. It balances the pushing 
force and therefore the box does not move. 
In [Fig. 15.2(b)] two children push the box 
harder but the box still does not move. This 
is because the frictional force still balances 
the pushing force. If the children push the 
box harder still, the pushing force becomes 
bigger than the frictional force [Fig. 15.2. 



(c)]. There is an imbalanced force. So, the 
box starts moving. 

15.2 First law of motion 

Galileo observed the motion of objects on 
an inclined plane. He deduced that objects 
move with a constant speed when no force 
acts on them. 



^m 


■ Name 


Galileo 


Ej 


B Born 


15 February 1564 


Wn 


B Birth place 


Grand Duchy of Tuscany, Italy 


V^ 


W Died 


8 January 1642 


H 


■1 Best known for 


Astronomy, physics 
and mathematics 



Newton studied Galileo's ideas on 
force and motion and presented three 
fundamental laws that govern the motion 
of objects. These three laws are known as 
Newton's Laws of Motion. The first law of 
motion is stated as: 

An object remains in the state of 
rest or of uniform motion in a straight 
line unless compelled to change that 
state by an applied unbalanced force. 

In other words, all objects resist a change 
in their state of motion. The tendency of 
undisturbed objects to stay at rest or to 
keep moving with the same velocity is 
called inertia. This is why, the first law of 
motion is also known as the law of inertia. 

Certain experiences that we come 
across while travelling in a motor car 
can be explained on the basis of the law 
of inertia. We tend to remain at rest with 
respect to the seat until the driver applies 
a braking force to stop the motor car. With 
the application of brakes, the car slows 
down but our body tends to continue in the 
same state of motion because of inertia. 
A sudden application of brakes may thus 
cause injury to us by collision with panels 
in front. 



LAWS OF MOTION AND GRAVITATION 



U 



An opposite experience is encountered 
when we are standing in a bus which 
begins to move suddenly. Now we tend to 
fall backwards. This is because a sudden 
start of the bus brings motion to the bus 
as well as to our feet in contact with the 
floor of the bus. But the rest of our body 
opposes this motion because of its inertia. 

When a motor car makes a sharp turn 
at a high speed, we tend to get thrown to 
one side. This can again be explained on 
the basis of the law of inertia. We tend to 
continue in our straight line motion. When 
an unbalanced force is applied by the 
engine to change the direction of motion of 
the motor car, we move to one side of the 
seat due to the inertia of our body. 

Inertia of a body can be illustrated 
through the following activities. 



ACTIVITY 15.1 



Make a pile of similar carrom coins on 
a table as shown in Fig. 15.3. 




Fig. 15.3: 

11 IT 

Attempt a sharp horizontal hit at the 
bottom of the pile using another carom 
coin or the striker. If the hit is strong 
enough, the bottom coin moves out 
quickly. Once the lowest coin is 
removed, the inertia of the other coins 
makes them 'fall' vertically on the 
table. 



15.3. INERTIA AND MASS 

All the examples and activities given 
so far, illustrate that there is a resistance 



offered by an object to change its state of 
motion. If it is at rest, it tends to remain at 
rest. If it is moving it tends to keep moving. 
This property of an object is called inertia. 
Therefore the inability of a body to 
change its state of rest or of uniform 
motion by itself is called inertia. 

Inertia of body depends mainly upon 
its mass. If we kick a foot ball, it flies away. 
But if we kick a stone of the same size with 
equal force, it hardly moves. We may, in fact 
get an injury in our foot. A force, that is just 
enough to cause a small carriage to pick 
up a large velocity, will produce a negligible 
change in the motion of a train. We say 
that train has more inertia than the carriage 
Clearly, more massive objects offer larger 
inertia. The inertia of an object is measured by 
its mass. 

15.4 MOMENTUM 

Let us recount some observations from 
our everyday life. During the game of 
table tennis, if a ball hits a player, it does 
not hurt him. On the other hand, when 
fast moving cricket ball hits a spectator, 
it may hurt him. A truck at rest does not 
require any attention when parked along 
a roadside. But a moving truck, even at a 
very low speed, may kill a person standing 
in its path. A small mass such as a bullet 
may kill a person when fired from a gun. 
These observations suggest that the 
impact produced by an object depends 
on its mass and velocity. In other words, 
there appears to exist some quantity of 
importance that combines the object's 
mass and velocity. One such property 
called momentum was introduced by 
Newton. The momentum 'p'ofan object 
is defined as the product of its mass 
'm' and velocity V\ That is,p=mv 



Momentum has both direction and 
magnitude. It is a vector quantity. Its 
direction is same as that of the velocity. 
The SI unit of momentum is kg ms"\ 

15.5 SECOND LAW OF MOTION 

Let us consider a situation in which a car 
with a dead battery is to be pushed along 
a straight road to give it a speed of 1 m s-^ 
which is sufficient to start its engine. If 
one or two persons give a sudden push 
(unbalanced force) to it, it hardly starts. 
But a continuous push over it sometime 
results in a gradual acceleration of the 
car to the required speed. It means that 
the change of momentum of the car is not 
only determined by the magnitude of the 
force, but also by the time during which 
the force is exerted. It may then also 
be concluded that the force necessary 
to change the momentum of the object 
depends on the time rate at which the 
momentum is changed. 

The second law of motion states that 
the rate of change of momentum of an 
object is proportional to the applied 
unbalanced force in the direction of 
force. Suppose an object of mass 'm' is 
moving along a straight line with an initial 
velocity 'u'. It is uniformly accelerated to 
velocity V in time 't' by the application 
of constant force, 'F' throughout the 
time, T. 

Initial momentum of the object = mu 

Final momentum of the object = mv 

The change in = mv - mu = m(v - u) (1) 
momentum 



Change of momentum 

Rate of change = 

of momentum time 



m (v-u) 



(2) 



t 

According to Newton II law of motion, this 
is nothing but applied force. 

m(v-u) 
Therefore the applied force, F = 



t 



v-u 



But the acceleration, 



a = 



t 



(which is the rate of change of velocity). 

The applied force, F a ma 

F = Kma (3) 

'K' is known as the constant of 
proportionality. The SI unit of mass and 
acceleration are kg and m s"^ respectively. 
The unit of force is so chosen that the value 
of the constant 'K' becomes one. 

Therefore, F = ma (4) 

1 unit of force = (1 kg) x (1 m s^) 

The unit of force is kg m s-^ or nei/i/fon 
which has the symbol 'N'. 

One unit of force(1N) is defined as 
the amount of force that produces an 
acceleration of 1 m s ^ in an object of 1 
kg mass. 

The second law of motion gives us a 
method to measure the force acting on 
an object as a product of its mass and 
acceleration. 



LAWS OF MOTION AND GRAVITATION 



U 



Example:15.1 

A constant force acts on an object of 
mass 1 kg for a duration of 4 s. It increases 
the objects velocity from 2 ms"^ to 8 m s"^ 
Find the magnitude of the applied force. 

Solution: 

Given, mass of the object m = 10 kg 

Initial velocity u = 2 m s-^ 

Final velocity v = 8 m s"^ 

m(v - u) 
We know, force F = - 



10 (8-2) 



t 
10x6 



F = 



= 15N 



4 4 

Example:15.2 

Which would require a greater force for 
accelerating a 2 kg of mass at 4 m s"^ or a 
3 kg mass at 2 m s-^? 

Solution 

We know, force F = ma 

Given, m^ = 2 kg a^ = 4 m s^ 

m^ = 3 kg a^ = 2 m s-^ 

Thus, F^ = m^ a^ = 2 kg X 4 m s-2 = 8 N 

and F^ = m^ a2 = 3 kg X 2 m s-2 = 6 N 

^ F^ > F, 

Thus, accelerating a 2 kg mass at 4m s-^ 
would require a greater force. 

15.6 THIRD LAW OF MOTION 

Let us consider two spring balances 
connected together as shown in Fig. 15.4 

aIt^ "- 



immmr zz^ 



F\g. ISA 



^1 I 

I I I M M 



The fixed end B of the balance is 
attached with a rigid support like a wall. 
When a force is applied through the free 
end of the spring balance A, it is observed 
that both the spring balances show the 
same readings on their scales. It means 
that the force exerted by spring balance 
A on balance B is equal but opposite in 
direction to the force exerted by the balance 
B on balance A. The force which balance 
A exerts on balance B is called action and 
the force of balance B on balance A is 
called the reaction. 

Newton's third law of motion states that 
for every action there is an equal and 
opposite reaction. It must be remembered 
that the action and reaction always act on 
two different objects. 

When a gun is fired it exerts forward force 
on the bullet. The bullet exerts an equal and 
opposite reaction force on the gun. This 
results in the recoil of the gun. Fig. 15.5 

Recoil force 
on the gun 




Accelerating force 
on the bullet 



Fig. 15.5 



Since the gun has a much greater mass 
than the bullet, the acceleration of the gun is 
much less than the acceleration of the bullet. 

15.7 CONSERVATION OF 

MOMEN-TUM AND PROOF 

The law of conservation of momentum 
states that, in the absence of external 
unbalanced force the total momentum of 
a system of objects remains unchanged 
or conserved by collision. 



Consider two objects (two balls) A and 
B of masses 'm^' and 'm^' are traveling in 
the same direction along a straight line at 
different velocities 'u^' and 'u^' respectively 
Fig. 15. 6(a) .There are no other external 
unbalanced forces acting on them . Let 
u^ > u^ and the two balls collide with each 
other as shown in Fig. 15.6(b). During 
collision which last for time T , the ball A 
exerts a force F^ on ball B , and the ball 
B exerts a force F^ on ball A. Let v^ and v^ 
be the velocities of two balls A and B after 
collision respectively in the same direction 
as before collision, Fig 15.6(c). 



A B 

(a) 



Before collision 



Fi F2 

®© 

A B 

(b) 

During collision 

A B 

(C) 

After collision 
Fig. 15.6 

According to Newton second law of motion 



The force acting 

on B (action) F^ = mass of B X 

acceleration on B. 

m^ (V2-U2) 

F, = (1) 

t 

The force acting 

on A (reaction) F^ = mass of A X 

acceleration on A. 

nil (vr^i) 
(2) 



^2 = 



t 



According to Newton's third law of motion 
From equation (1) and (2) 



m^ (v^-u^) - m^ (v^-u^) 



t t 

^2 (^2 - U2) = -m^ (v,-u^) 



m^v^ - m2U2 = -nri^v^ + m^u^ 



m^v^ + m^v^ = m^u^ + m^u^ 

Therefore, 

m^u^ + m^u^ = m^v^ + m^v^ 

The total momentum before collision 
is equal to the total momentum after 
collision. The total momentum of two 
objects remain unchanged due to collision 
in the absence of external force. This law 
holds good for any number of objects. 



ACTIVITY 15.2 



Take a big rubber balloon and inflate 
it fully.Tie its neck using a thread. 



LAWS OF MOTION AND GRAVITATION 



bJ 



ACTIVITY 15.2 



Also using adhesive tape, 

fix a straw on the surface of this 

balloon. 

Pass a thread through the straw 
and hold one end of the thread in 
your hand or fix it on the wall. 

Ask your friend to hold the other 
end of the thread or fix it on 
a wall at some distance. This 
arrangement is shown in Fig. 15.7 

Now remove the thread tied on 
the neck of the balloon. Let the 
air escape from the mouth of the 
balloon. 

Observe the direction in which 
the straw moves. 

STRAW 



so; 



Air 



BALOON 



Fig. 15.7 



Example:15.3 

A bullet of mass 15g is horizontally fired 
with a velocity 100 m s"^ from a pistol of 
mass 2 kg what is the recoil velocity of the 
pistol? 

Solution: 

The mass of bullet, m^ = 15 g = 0.015 kg 
Mass of the pistol, m^ = 2 kg 
Initial velocity of the bullet, u^ = 
Initial velocity of the pistol, u^ = 
Final velocity of the bullet, v^ = + 100 m s'^ 
(The direction of bullet is taken from left to 



right-positive, by convention) 

Recoil velocity of the pistol, = v 

Total momentum of the pistol and bullet 
before fire, 

= (0.015 X + 2 X 0) kg m s-^ 

= kg m s"^ 

Total momentum of the pistol and bullet 
after fire, 

= (0.015 X 100 + 2 X V) 

= (1.5 + 2v) kg m s-i 

According to the law of conservation of 
momentum. 

Total momentum after fire = total 
momentum before fire 

1.5 + 2v = 

2v = -1.5 

V = -0.75 m s"^ 

Negative sign indicates that the direction 
in which the pistol would recoil is opposite 
to that of the bullet, that is, right to left. 

15.8 MOMENT OF FORCE AND 
COUPLE 

Moment of a force 

A force can rotate a nut when applied 
by a wrench or it can open a door while the 
door rotates on its hinges. In addition to the 
tendency to move a body in the direction 
of the application of a force, a force also 
tends to rotate the body about any axis 
which does not intersect the line of action 
of the force and also not parallel to it. This 
tendency of rotation is called turning effect 
of a force or moment of the force about the 
given axis. The magnitude of the moment 
of force F about a point is defined as the 
product of the magnitude of force and 



the perpendicular distance of the point 
from the line of action of the force. 

Let us consider a force F acting at the 
point P on the body as shown in Fig. 15.8 




Fig. 15.8 



Then, the moment of the force F about 
the point O = IVIagnitude of the force 
X perpendicular distance between the 
direction of the force and the point about 
which moment is to be determined = F x d. 

If the force acting on a body rotates 
the body in anticlockwise direction with 
respect to O then the moment is called 
anticlockwise moment. On the other hand, 
if the force rotates the body in clockwise 
direction then the moment is said to be 
clockwise moment. The unit of moment of 
the force is N m. 



O 



-^-f 



o 



----^--l 



Fig. 15.9 



As a matter of convention, an 
anticlockwise moment is taken as positive 
and a clockwise moment as negative. 

Couple 

There are many examples in practice 
where two forces, acting together, exert a 
moment or turning effect on some object. 
As a very simple case, suppose two 
strings are tied to a wheel at the points X 
and Y, and two equal and opposite forces, 
'F' are exerted tangentially to the wheels 
(Fig. 15.10). If the wheel is pivoted at its 
centre O it begins to rotate about O in an 
anticlockwise direction. 




Fig. 1 5.10 

Two equal and opposite forces whose 
lines of action do not coincide are said to 
constitute a couple in mechanics. 

15.9. GRAVITATION 



^uu 


Name 


Isaac Newton 




Born 

Birtii Place 
Died 


4 January 1643 
Woolsthrope, England 
20 March 1727 


mm 


Best Known as 


The genius who explained 
gravity. 



We always observe that an object dropped 
from a height falls towards the earth. It is 
said that Newton was sitting under the tree, 
an apple fell on him. The fall of the apple 
made Newton start thinking. It is seen that 
a falling apple is attracted towards the 



LAWS OF MOTION AND GRAVITATION 



U 



earth. Does the apple attract the earth? If 
so we do not see earth moving towards an 
apple. Why? 

According to Newton's Third Law of 
Motion, the apple does attract the earth. 
But according to Second Law of motion, 
for a given force, acceleration is inversely 
proportional to the mass of the object. 
The mass of an apple is negligibly small 
compared to that of the earth. So we do 
not see the earth moving towards the 
apple. We know that all planets go around 
the sun. Extend the above argument for 
all planets in our solar system. There exist 
a force between sun and the planets. 
Newton concluded that all objects in 
the universe attract each other. This 
force of attraction between objects is 
called the gravitational force. 



ACTIVITY 15.3 



Take a piece of thread. Tie a small 
stone atone end. 

Hold the other end of the thread and 
whirl it round as shown in Fig. 15.11. 

Note the motion of the stone. 

Release the thread. 

Again note the direction of motion of 
the stone. 




It is noted that the stone describes a 
circular path with a velocity of constant 
magnitude. 

15.9.1. Newton law of gravitation 

Every object in the universe attracts every 
other object with a force which is directly 
proportional to the product of their masses 
and inversely proportional to the square 
of the distance between them. The force 
acts along the line joining the centers of 



two objects. 

mi 



1712 



Fig. 15.12 

Let two objects A and B of masses m^, 
m^ respectively lie at a distance 'd' from 
each other as shown in Fig. 15. 12. Let the 
force of attraction between two objects is 
'F'. According to above law. 



F (X m^m^ 



Combining (1)and (2) 



Fx 



m^m2 



or 



F = - 



Gm,m. 



(1) 
(2) 

(3) 
(4) 



Where G is the constant of proportionality 
and is called the Universal gravitation 
constant. From eqn (4) 

F.d2 
G= 



m^m2 



Fig 15.11. 



Substituting the S.I units in this equation 
the unit of G is found to be N m^kg-^ 
The value of G is 6.673x10" N m^kg^ 



15.9.2 Mass 

Mass is the amount of matter present in a 
body (or) is a measure of how much matter 
an object has. 

15.9.3 Weight 

Weight is the force which a given mass 
feels due to the gravity at its place (or) is 
a measure of how strongly gravity pulls on 
that matter. 

If you were to travel to the moon, your 
weight would change because the pull of 
the gravity is weaker there than on the 
earth, but your mass would stay the same 
because you are still made up of the same 
amount of matter. 

Example 15.4 

Mass of an object is 5 kg. What is its weight 
on the earth? 

Solution: 

Mass, m = 5 kg 

Acceleration due to gravity, g = 9.8 m s-^ 

Weight, w = m x g 

w = 5 kg X 9.8 m s^ = 49 N 

Thus the weight of the object is, 49 N 

Difference between mass and weight 



Mass 


Weight 


1. Fundamental 
quantity. 


Derived quantity. 


2. It is the 
amount of 
matter con- 
tained in a 
body. 


It is the 

gravitational pull 
acting on the 
body. 


3. Its unit is 
kilogram. 


It is measured in 
newton. 



4. Remains the 


Varies from 


same. 


place to 




place. 


5. It is measured 


It is measured 


using physical 


using spring 


balance. 


balance. 



15.9.4 Acceleration due to gravity 

Galileo was the first to make a 
systematic study of the motion of a 
body under the gravity of the Earth. He 
dropped various objects from leaning 
tower of Pisa and made analysis of their 
motion under gravity. He came to the 
conclusion that "in the absence of air, 
all bodies will fall at the same rate". 
It is the air resistance that slows down 
a piece of paper or a parachute falling 
under gravity. If a heavy stone and a 
parachute are dropped where there 
is no air, both will fall together at the 
same rate. 

Experiments showed that the 
velocity of a freely falling body under 
gravity increases at a constant rate, 
(i.e.) with a constant acceleration. The 
acceleration produced in a body on 
account of the force of gravity is 
called acceleration due to gravity. It 
is denoted by g. At a given place, the 
value of g is the same for all bodies 
irrespective of their masses. It differs 
from place to place on the surface of 
the Earth. It also varies with altitude 
and depth. 

The value of g at sea-level and at a 
latitude of 45° is taken as the standard 
free -fall acceleration (i.e.) g=9.8 m s-^ 



LAWS OF MOTION AND GRAVITATION 



bJ 



Acceleration due to gravity at the 
surface of the earth 

Consider a body of mass 'm' on the surface 
of the earth as shown in Fig. 15.13. 
m 




Fig. 15. 13 

Its distance from the centre of the Earth 
is R (radius of the Earth). 

The gravitational force experienced by the 

body is F = ^^^ where M is the 
R2 

mass of the earth. From Newton's 
second law of motion, 

Force, F = mg 

Equating the above two forces, 

GMm 

F = = mg 

R2 

Therefore, GM 

g = 



This equation shows that 'g' is 
independent of the mass of the body 'm' 
but, it varies with the distance from the 
centre of the Earth. If the Earth is assumed 
to be a sphere of radius R, the value of 'g' 
on the surface of the Earth is given by 
GM 

g = — 



15.9.5. Mass of earth 

From the expression g = GM/R^ the mass 
of the Earth can be calculated as follows: 



M = 



gR^ 



M = 9.8 X (6.38 X 10^)2/6.67 x lO^i 
M = 5.98 X 10^^ kg. 

Science today 

Chandrayaan 




Mylswamy Annadurai born on 
2"^ July 1958 is a household name 
in this part of the country .People 
fondly associate his name with 
chandrayaan to the extent it has 
almost become his middle name. 
He obtained his M.E Degree in 
Electronics in 1982. In the same 
year he joined in ISRO. 

Annadurai is a leading 
technologist in the field of 
satellite system. Currently 
Annadurai serves as the Project 
Director of Chandrayaan-1 and 
Chandrayaan-2. He has made 
significant contribution to the cost 
effective design of Chandrayaan. 
Through his inspiring speeches 
he has become a motivating force 
among the Indian students. 



CHANDRAYAN 



ENERGETIC ^^,^ 

MEUTRAL ANALYSER ^VVIM 



RADOM 




MNI-SAR 



Chandrayaan-1 is a moon-traveler or 
moon vehicle. It was Indian's first 
unmanned lunar probe. It was launched 
by Indian Space Research Organization 
in October 2008 from Srihari Kota in 
Andrapradesh and operated until August 
2009. The mission included a lunar orbiter 
and an impactor. It carried five ISRO 
payloads and six payloads from other 
space agencies including NASA, 
European Space Agencies(ESA), and the 
Bulgarian Aerospace Agency which were 
carried free of cost. 

Chandrayaan operated for 3 1 2 days and 
achieved 95% of its planned objectives. 
The following are its achievements, 

• The discovery of wide spread presence 
of water molecules in lunar soil. 

• Chandrayaan's Moon Mineralogy 
Mapper has confirmed that moon was 
once completely molten. 

• European Space Agency payload- 
Chandrayaan-1 imaging X-ray 
spectrometer (CXIS)-detected more 
than two dozen weak solar flares 
during the mission. 

• The terrain mapping camera on board 
Chandrayaan-1 has recorded images 



of the landing site of US space craft 
Apollo-15, Apollo-11. 

• It has provided high-resolution spectral 
data on the mineralogy of the moon. 

• Lunar Laser Ranging Instrument 
(LLRI) covered both the Lunar Poles 
and additional lunar region of interest. 

• The X-ray signatures of aluminum, 
magnesium and silicon were picked 
up by the CXIS X-ray camera 

• The Bulgarian payload called Radiation 
Dose Monitor (RADOM) was activated 
on the day of launch itself and worked 
till the mission end. 

• More than 40000 images have been 
transmitted by Chandrayaan Camera 
in 75 days. 

• The Terrain Mapping Camera acquired 
images of peaks and Craters. The 
moon consists of mostly of Craters. 

• Chandrayaan beamed back its first 
images of the Earth in its entirety. 

• Chandrayaan-1 has discovered large 
caves on the lunar surface that can 
act as human shelter on the moon. 

Cryogenic techniques 

The word cryogenics terms from Greek 
and means "the production of freezing 
cold". 

In physics cryogenics is the study of 
the production of very low temperature 
(below 123K); and the behaviour of 
materials at those temperature. A 
person who studies elements under 
extremely cold temperature is called a 
cryogencist. Cryogenics use the Kelvin 
scale of temperature. Liquefied gases 
such as liquid nitrogen, liquid helium is 
used in many cryogenic applications. 



LAWS OF MOTION AND GRAVITATION 



U 



Liquid nitrogen is the most commonly 
used element in cryogenics and is legally 
purchasable around the world. Liquid 
helium is also commonly used and allows 
for the lowest attainable temperature to be 
reached. These liquids are held in special 
containers called Dewar flasks which are 
generally about six feet tall and three feet 
in diameter. 

The field of cryogenics advanced 
during world war-2. Scientist found that 
metals frozen to low temperature showed 
more resistance to wear. This is known 
as cryogenic hardening. The commercial 
cryogenic processing industry was 
founded in 1966 by Ed Busch; and merged 
several small companies later to form 
oldest commercial cryogenic company in 
the world. They originally experimented 
with the possibility of increasing the life of 
metal tools. 

Cryogens like liquid nitrogen are further 
used for specially chilling and freezing 
applications. 

(i) Rocket 

The important use of cryogenics is 
cryogenic fuels. Cryogenic fuels mainly 
liquid hydrogen has been used as rocket 
fuel. 

(ii) Magnetic Resonance Imaging (MR!) 

MR! is used to scan inner organs of 
human body by penetrating very intense 
magnetic field. The magnetic field is 
generated by super conducting coils with 
the help of liquid helium. It can reduce the 
temperature of the coil to around 4k. At 
this low temperature very high resolution 
images can be obtained. 

(iii) Power transmission in big cities: 



It is difficult to transmit power by over 
head cables in cities. So underground 
cables are used. But underground cables 
get heated and the resistance of the wire 
increases leading to wastage of power. 
This can be solved by cryogenics. Liquefied 
gases are sprayed on the cables to keep 
them cool and reduce their resistance. 

(iv) Food Freezing: 

Cryogenic gases are used in 
transportation of large masses of frozen 
food, when very large quantity of food must 
be transported to regions like war field, 
earthquake hit regions etc., they must be 
stored for. 

(v) Vaccines: 

The freezing of biotechnology products 
like vaccines require nitrogen freezing 
systems. 

Space station: 

A space station is an artificial structure 
designed for humans to live and work in 
outer space for a period of time. 

Current and recent-history space 
stations are designed for medium-term 
living in orbit, for periods of weeks, months 
or even years. The only space stations are 
Almaz and Salyut series. Sky lab and Mir. 




Space stations are used to study the 
effects of long-space flight on the human 



body. It provides platforms for greater 
number and length of scientific studies 
than available on other space vehicles. 
Space stations have been used for both 
military and civilian purposes. The last 
military-used space station was Salyut 5, 
which was used by the Almaz program of 
the Soviet Union in 1976 and 1977. 

Broadly speaking the space stations so 
for launched has been of two types. Salyut 
and Skylab have been "monolithic." They 
were constructed and launched in one 
piece, and then manned by a crew later. 
As such, they generally contained all their 
supplies and experimental equipment 
when launched, and were considered 
"expended", and then abandoned, when 
these were used up. 

Starting with Salyut 6 and Salyut 7, a 
change was seen. These were built with 
two docking ports. They allowed a second 
crew to visit, bringing a new space craft 
with them. 

This allowed for a crew to man the station 
continually, sky lab was also equipped with 
two docking ports, but the extra port was 
never utilized. The presence of the second 
port on the new station allowed progress 
supply vehicle to be docked to the station, 
meaning that fresh supplies could be 
brought to aid long-duration missions. 

The second group, Mir and the 
International Space Station (ISS), have 
been modular; a core unit was launched. 



and additional modules, generally with 
a specific role, were later added to that, 
(on Mir they were usually launched 
independently, whereas on the ISS most 
are brought by the Space Shuttle). This 
method allows for greater flexibility in 
operation. It removes the need for a single 
immensely powerful launch vehicle. These 
stations are also designed from the outset 
to have their supplies provided by logistical 
support, which allows for a longer lifetime 
at the cost of requiring regular support 
launches. 

These stations have various issues 
that limit their long-term habitability, such 
as very low recycling rates, relatively high 
radiation levels and a lack of gravity. Some 
of these problems cause discomfort and 
long-term health effects. 

Future space habitats may attempt to 
address these issues, and are intended 
for long-term occupation. Some designs 
might even accommodate large number of 
people, essentially "cities in space" where 
people would make their homes. No such 
design has yet been constructed, even for 
a small station; the current (2010) launch 
costs are not economically or politically 
viable. 

The People's Republic of China is 
expected to launch its space station 
named Tiangong 1 , in the first half of 201 1 . 
This would make China the third country to 
launch a space station. 



EVALUATION 



PART A 

1. The acceleration in a body is due to 



(balanced force, un-balanced force. 



electro static force) 

The physical quantity which is equal 
to rate of change of momentum is 
(displacement, acceleration, force, 
impulse) 



LAWS OF MOTION AND GRAVITATION 



bJ 



3. The momentum of a massive object at 
rest is . 

(very large, very small, zero, infinity) 

4. The weight of 50 kg person at the 
surface of earth is . 

(SON, 35 N, 380 N, 490 N) 

5. The freezing of biotechnology products 

like vaccines require freezing 

systems. 

(Helium, Nitrogen, Ammonia, Chlorine) 

PART - B 

1. From the following statements write 
down that which is not applicabel to 
mass of an object 

a. It is a fundamental quantity 

b. It is measured using physical 
balance, c. It is measured using 
spring balance. 

2. Fill in the blanks. 

a) Force = mass x acceleration, then 
momentum = ? 



b) Liquid hydrogen is for rocket, then 

forMRI. 

3. The name of some organisations which 
are associated with Chandrayan-I 
mission are given below, but some of 
them are not. List out the wrong ones. 

(ISRO, BARC, NASA, ESA, WHO, 
ONGC) 

4. Correct the mistakes, if any, in the 
following statements. 

a. One newton is the force that produces 
an acceleration of 1 ms-^ in an object 



of 1 gram mass. 

b. Action and reaction is always acting 
on the same body. 

The important use of cryogenics is 
cryogenic fuels. What do you mean by 
cryogenic fuels? 

As a matter of convention, an 
anticlockwise moment is taken as 

and a clockwise moment is 

taken as 



PART - C 

1 . a) Newton's first law of motion gives a 
qualitative definition offeree. Justify. 



Fi F2 



10 m/s 5 m/s 1^ ^ 

ho Kgj-^( 20 Kg J -► (lO KgY 20 Kg J n.0 Kg) -►[ 



V^^4m/s 

( 20KgW 

b) The figure represents two bodies 
of masses 10 kg and 20 kg and 
moving with an initial velocity of 
10 ms"^ and 5 ms"^ respectively. 
They are colliding with each other. 
After collision they are moving 
with velocities 12 ms"^ and 4 ms"^ 
respectively. The time of collision 
be .2 s. Then calculate F^ and F^. 

2. a) Space stations are used to study 
the effects of long-space flight on 
the human body, justify. 

b) F=G m^ m^ / d^ is the mathematical 
form of Newton's law of gravitation, 
G - gravitational constant, m^ 
m^, are the masses of two bodies 
separated by a distance d, then 
give the statement of Newton's law 
of gravitation. 



FURTHER REFERENCE1 



Books : 1. Advanced physics by : M. Nelkon and P. Parker, C.B.S publications 
L 2. College Physics by : R.L.Weber, K.V. Manning, Tata McGraw Hill 

Websites: www.brittannica.com I www.zonaland education.com I www.wiki.animers.com 



Chapter 






li^ 







ELECTRICITY AND 
ENERGY 



ELECTRICITY AND ENERGY 




16 ELECTRICITY AND ENERGY 



Name 


: Michael Faraday ^H 


Born 


: 22 September 1791 ^M 


Birth place 


: Newington, England ^H 


Died 


: 25 August 1867 Kg 


Best known as 


: Inventor of the first dynamo 



Electricity has an important place in mod- 
ern society. It is a controllable and con- 
venient form of energy for variety of uses 
in homes, schools, hospitals, industries 
and so on. What constitutes electricity? 

How does it flow in an electric circuit? 
What are the factors that regulate elec- 
tricity through an electric circuit?. In this 
chapter we shall attempt to answer such 
questions. 

16.1. ELECTRIC CURRENT 
AND CIRCUIT 

We are familiar with air current and water 
current. We know that flowing water con- 
stitute water current in rivers. Similarly if 
the electric charge flows through a con- 
ductor (metallic wire), we say that there is 
an electric current in the conductor. In a 



torch we know that a battery provide flow 
of charges or an electric current through a 
torch bulb to glow. We have also seen that 
it gives light only when it is switched on. 
What does a switch do? A switch makes a 
conducting link between the cell and the 
bulb. A continuous and closed path of 
an electric current is called an electric 
circuit Now if the circuit is broken any- 
where the current stops flowing and the 
bulb does not glow. 

How do we express electric current? 
Electric current is expressed by the 
amount of charge flowing through a 
particular area of cross section of a 
conductor in unit time. In other words 
it is the rate of flow of electric charges. 
In circuit using metallic wires, electrons 
constitute flow of charges. The direction 
of electric current is taken as opposite to 
the direction of the flow of electrons. 

If a net charge Q, flows across any 
cross-section of a conductor in time t, then 
the current I through the cross-section is 

l=Q/t 



The S.I unit of electric charge is cou- 
lomb. This is equivalent to the charge 
contained in nearly 6x10^^ electrons. 
The electric current is expressed by a 
unit called ampere (A), named after the 
French Scientist. 

From the above equation, 

When Q = 1 C, t = Is, I=1A. 

When one coulomb of charge flows 
in one second across any cross section 
of a conductor, the current in it is one 
ampere. An instrument called ammeter is 
used to measure current in a circuit. 

Example 16.1 

A current of 0.75 A is drawn by a 
filament of an electric bulb for 1 minutes. 
Find the amount of electric charge that 
flows through the circuit. 



Solution: 




Given, 


1 =0.75 A, 




t = 10 minutes = 600 s 


We know, 


Q = \xt 




= 0.75 Ax 600s 




Q = 450 C 



The Fig. 16.1 shows a schematic 
diagram of an electric circuit comprising 
battery, bulb, ammeter and a plug key. 

Bulb 



C 



Bt k 

Fig. 16.1 Electric circuit 



16.2. ELECTRIC POTENTIAL 
AND POTENTIAL 
DIFFERENCE 

What makes the electric charge to flow? 
ter. Charges do not flow in a copper wire 
by themselves, just as water in a perfectly 
horizontal tube does not flow. One end of 
the tube is connected to a tank of water. Now 
there is a pressure difference between the 
two ends of the tube. Water flows out of the 
other end of the tube. For flow of charges 
in a conducting metallic wire, the electrons 
move only if there is a difference of electric 
pressure-called potential difference-along 
the conductor. This difference of potential 
may be produced by a battery, consisting of 
one or more electric cells. When the cell is 
connected to a conducting circuit element, 
the potential difference sets the charges in 
motion in the conductor and produces an 
electric current. 

We define the electric potential 
difference between two points in an 
electric circuit carrying some current 
as the work done to move a unit charge 
from one point to the other. 

Potential difference (V) between two 
points = work done (W)/charge (Q). 

V = W/Q 

The S.I Unit of potential difference is volt 
(V). 

1 volt= 1 joule/1 coulomb 

One volt is the potential difference 
between two points in a current 
carrying conductor when 1 joule of 
work is done to move a charge of 
1 coulomb from one point to the other. 



ELECTRICITY AND ENERGY 




The potential difference is measured by 
means of an instrument called voltmeter. 



16.3. CIRCUIT DIAGRAM 

The Schematic diagram, in which 
different components of the circuit are 
represented by the symbols conveniently 
used, is called a circuit diagram. 
Conventional symbols used to represent 
some of the most commonly used electrical 
components are given in table 16.1. 



COMPO- 
NENTS 



An electric 
cell 



A battery or a 
combination 
of cells 



Plug key or 
switch (open) 



Plug key 
or switch 
(closed) 



A wire joint 



Wires cross- 
ing without 
joining 



Electric bulb 



A resistor of 
resistane R 



Variable 
resistance or 
rheostat 



Ammeter 



Voltmeter 



SYMBOLS 



■^» 



H' \^ 1^ 



i y 



■<•> 



f 



_nn_ or ^ 



— sNW^ 



— ^)^^ — 



or 



— TVW^ 
^<A>- 



■^<V>- 



Example 16.2. 

How much work is done in moving a 
charge of 5 C across two points having a 
potential difference 10 V? 

Solution: 

Given charge, Q = 5 C 

Potential difference, V = 1 V 

The amount of work done 
in moving the charge, W = V x Q 

W= 10 V X 5C = 50 J 

16A OHM'S LAW 

is there a relationship between the poten- 



Name 


: George Sinnon Ohm 




^^f^' '^^^M 


Born 


: 16 March 1789 


K- ~'^| 


Birth place 


: Eriangen, Germany 


InMH 


Died 


: 06 July 1854 


Ha '>'^i^^HU^^I^H 


Best known for 


: Ohm's law 


^^^M 



Table 16.1. 



tial difference across a conductor and the 
current through it? .Let us explore with an 
activity. 



ACTIVITY 16.1 



Set up a circuit as shown in Fig. 
16.2. consisting of a nichrome 
wire XY of length say 0.5m, an 
ammeter, a Voltmeter and four 
cells of 1.5V each. (Nichrome 
is an alloy of nickel, chromium, 
manganese and iron metals). 

First use only one cell as 
the source in the circuit. Note 
the reading in the ammeter I, 
for the current and reading of 
the voltmeter V for the potential 
difference across the nichrome 
wire XY in the circuit. Tabulate 
them in the table given. 



ACTIVITY 



Repeat the above steps using 
two, three cells and then four cells 
in the circuit separately. 

Calculate the ratio of V to I for 
each pair of potential difference V 
and current I. 

+V V V V- 



r^ T^T'"M'i ^ 



Si^ 



y •^*rr\- 



MAAAM/V>^ 



+"^- 



Fig. 16.2 



In this activity you will find the ratio V/l 
is a constant. 

In 1827, a German Physicist George 
Simon Ohm found out the relationship 
between the current I flowing in a metal- 



lic wire and the potential difference across 
its terminals. 

Ohm's law states that at constant 
temperature the steady current (I) 
flowing through a conductor is directly 
proportional to the potential difference 
(V) between its ends. 

V(x I (or) V/l=constant. 

Example 16.3 

The potential difference between the 
terminals of an electric heater is 60 V 
when it draws a current of 5 A from the 
source. What current will the heater draw 
if the potential difference is increased to 
120 V? 

Solution: 

Given the potential difference, V = 60 V 

Current, I = 5 A, 

According to ohm's law, 

R = V/I = 60V/5A=12Q 

When the potential difference is 
increased to 120 V, the current is given by 

I=V/R=120V/12Q = 10A 



S.No 


Number of 
cells used in 
the circuit 


Current through 
the nichrome wire 
1 (ampere) 


Potential 

difference across 
the nichrome 
wire. V (volt) 


V/l 
(volt/ampere) 

Q 


1. 










2. 










3. 










4. 










5. 










6. 











ELECTRICITY AND ENERGY 




16.5. RESISTANCE OF A 

CONDUCTOR 

From Ohm's law, we know 

VocI, V = IR 

R is a constant for a given metallic wire 
at a given temperature and is called its re- 
sistance. It is the property of a conductor 
to resist the flow of charges through it. Its 
S.I unit is ohm, represented by the Greek 
letter Q. 

R = V/l, 1 ohm = 1 volt/1 ampere 

If the potential difference across the 
two ends of a conductor is 1volt and the 
current through it is lampere, then the 
resistance of the conductor is 1 ohm. 



ACTIVITY 16.2 



Set up the circuit by connecting 
four dry cells of 1 .5V each in series 
with the ammeter leaving a gap XY 
in the circuit, as shown in Fig. 16.3. 

Complete the circuit by connecting 
the nichrome wire in the gap 
XY. Plug the key. Note down the 
ammeter reading. Take out the 
key from the plug. 

Replace the nichrome wire with 
the torch bulb in the circuit and find 
the current through it by measuring 
the reading of the ammeter. 




Fig. 16.3 



ACTIVITY 



Now repeat the above steps with 
the LED bulb in the gap XY. 

Are the ammeter readings differ for 
different components connected 
in the gap XY? What do the above 
observations indicate? 



16.6. SYSTEM OF RESISTORS 

In various electrical circuits we often use 
resistors in various combinations. There 
are two methods of joining the resistors 
together. Resistors can be connected in 
series or in parallel. 

Resistors in series 

Consider three resistors of resistances 
R^, R^, R3 in series with a battery and a 
plug key as shown in Fig. 16.4. 



It R1 R2 R3 Y 



1/^ 



^^^' 



-V2 — ><-^3- 



H^O^H^^ 



K 



Sfl 



Fig. 16.4 

The current through each resistor is 
the same having a value I. The total po- 
tential difference across the combination 
of resistors in series is equal to the sum 
of potential difference across individual 
resistors. That is. 



v=v +v +v 

1 2 3 



(1) 



It is possible to replace the three re- 
sistors joined in series by an equivalent 



single resistor of resistance R^ such that 
the potential difference V across it, and 
the current I through the circuit remains 
the same. 

Applying ohm's law to the entire circuit 

we have, V=IR 

On applying ohm's law to the three 

resistors 

separately we further have 

V^=IR^ V2=IR2andV3=IR3 
Substituting these values in equation (1) 



(or) 



IR = IR^+IR2+IR3 



Rs = R1+R2+R3 



When several resistors are connected 
in series, the resistance of the combina- 
tion R^ is equal to the sum of their indi- 
vidual resistances R^, R^, R3 and is thus 
greater than any individual resistance. 

Example 16.4 

Two resistances 18 Q and 6 Q are con- 
nected to a 6 V battery in series. Calcu- 
late (a) the total resistance of the circuit, 
(b) the current through the circuit. 

Solution: 

(a) Given the resistance, R^ = 18 Q, 

R2 = 6Q 



The total resistance of the circuit F^= R^+F^ 

R3 = 18Q + 6Q = 24Q 

(b) The potential difference across 
the two terminals of the battery V = 6 V 

Now the current through the circuit, 

I = V/ R3 = 6 V / 24 Q 

= 0.25 A 



Resistors in parallel 

Considerthree resistors having resistances 
R^ R2 R3 connected in parallel. This 
combination is connected with a battery 
and plug key as shown in Fig. 16.5 

In parallel combination the potential 
difference across each resistor is the same 
having a value V. The total current I is 
equal to the sum of the separate currents 
through each branch of the combination. 



I = l,+ l,+ l3 



(1) 



Let R be the equivalent resistance of 




Fig. 16.5 

the parallel combination of resistors. By 
applying ohm's law to the parallel combi- 
nation of resistors we have I = V/R 

p 

On applying ohm's law to each resistor 
We have 

'i=V/R^, '2=V/R2andl3=V/R3 

Substituting these values in equation (1) 



(or) 



V/Rp=V/R^+V/R2+V/R3 
1/Rp=l/R^+1/R2+1/R3 



Thus the reciprocal of the equivalent 
resistance of a group of resistance joined 
in parallel is equal to the sum of the 
reciprocals of the individual resistance. 



ELECTRICITY AND ENERGY 




Example 16.5 

Three resistances having the values 
5 Q, 10 Q, 30 Q are connected parallel 
with each other. Calculate the total circuit 
resistance. 

Solution: 

Given, R^ = 5 Q , R^ = 10 Q.Rg = 30 Q 

These resistances are connected parallel 
Therefore, 1 / R = 1 / R + 1 / R + 1 / R, 

' p 12 3 

1 1 1 1 10 

R 5 10 30 30 

p 

30 

Rp=- =3Q 
10 

16.7. HEATING EFFECT OF 
ELECTRIC CURRENT 



ACTIVITY 16.3 



Take an electric cell, a bulb, a 
switch and connecting wires. 
Make an electric circuit as shown 
in Fig. 16.6. By pressing the key 
allow the current to pass through 
the bulb. 

The bulb gets heated when 
current flows continuously for a 
long time (when the key is on). 




Bulb 

Fig. 16.6 



We know that a battery is a source of 
electrical energy. Its potential difference 
between the two terminals sets the 
electrons in motion to flow the current 
through the resistor. To flow the current, 
the source has to keep spending its 
energy. Where does this energy go? 
What happens when an electric fan is 
used continuously for longer time? A 
part of the energy may be consumed into 
useful work (like in rotating the blades 
of the fan). Rest of the energy may be 
expended in heat to raise the temperature 
of the gadget. If the electric circuit is 
purely resistive, the source energy 
continuously gets dissipated entirely 
in the form of heat. This is known as 
heating effect of electric current. Heating 
effect of electric current has many useful 
appliances. The electric laundry iron, 
electric toaster, electric oven and electric 
heater are some of the familiar devices 
which uses this effect. 

16.8. JOULES LAW OF 
HEATING 

Consider a current I flowing through 
a resistor of resistance R. Let the po- 
tential difference across it be V. Let t 
be the time during which a charge Q 
flows across. The work done in moving 
the charge Q through the potential dif- 
ference V is VQ. Therefore the source 
must supply energy equal to VQ in time 
t. Hence the power input to the circuit 
by the source is 

P= V (Q/t) = VI 

or the energy supplied through the 
circuit by the source in time t is Pxt, that 
is Vlt. What happens to this energy ex- 



pended by the source? This energy gets 
dissipated in the resistor as heat. Thus for 
a steady current I, the amount of heat H 
produced in time t is 

H=Vlt 

Applying ohm's law we get H=P Rt. 

This is known as joules lawof heating. 
The law implies that heat produced in 
a resistor is (1) directly proportional 
to the square of current for a given 
resistance, (2) directly proportional to 
the resistance for a given current, and 
(3) directly proportional to the time for 
which the current flows through the 
resistor. 

Example 16.6 

A potential difference 20 V is applied 
across a 4 Q resistor. Find the rate of pro- 
duction of heat. 

Solution: 

Given potential difference, V = 20 V 
The resistance, R = 4 Q 

The time, t = 1 s 

According to ohm's law, I = V / R 
I =20V/4Q = 5A 

The rate of production of heat, H = PRT 
H = 52x4xlJ = 100 J 

16.9. ROLE OF FUSE 

A common application of joules heating 
is the fuse used in electric circuits. It 
consists of a piece of wire made of metal 
or an alloy (37% lead, 63% tin). It has 
high resistance and low melting point. 
The fuse is connected in series with the 
device. During the flow of any unduly high 



electric current the fuse wire melts and 
protects the circuits and appliances. 

16.10. DOMESTIC ELECTRIC 
CIRCUITS 

In our homes, we receive supply of 
electric power through a main supply (also 
called mains), either supported through 
overhead electric poles or by underground 
cables. One of the wires in the supply, 
usually with red insulation cover, is called 
live wire (or positive). Another wire, with 
black insulation, is called neutral wire (or 
negative). In our country, the potential 
differences between the two are 220 V. 

At the meter-board in the house, these 
wires pass into an electricity meter through 
a main fuse. Through the main switch 
they are connected to the line wires in 
the house. These wires supply electricity 
to separate circuits with in the house. 
Often, two separate circuits are used, one 
of 15A current rating for appliances with 
higher power ratings such as geysers , 
air coolers ,etc . The other circuit is of 5 
A current rating for bulbs, fans, etc. The 
earth wire which has insulation of green 
color is usually connected to a metal plate 
deep in the earth near the house. This 
is used as a safety measure, especially 
for those appliances that have a metallic 
body, for example, electric press, toaster, 
table fan, refrigerator, etc. The metallic 
body is connected to the earth wire, which 
provides a low-resistance conducting path 
for the current. Thus, it ensures that any 
leakage of current to the metallic body of 
the appliance keep its potential to that 
of the earth, and the user may not get a 
severe electric shock. 



ELECTRICITY AND ENERGY 




Fig. 16.7 gives a sciiematic diagram of 
one of tine common domestic circuits. In 
each separate circuit, different appliances 
can be connected across the live and 
neutral wires. Each appliance has a 
separate switch to 'ONTOFF' the flow 
of current through it. In order that each 
appliance has equal potential difference, 
they are connected parallel to each other. 









~rr\ 














\^ 






J 




/rTS 








^ 






• 




rr\ 






\e2/ 






^ 




"^ 








CsJ 
Csl 








E 
"o 

(D 
LU 












X 


ooo 
ooo 






C 



a 




% 

G 

C 




1 1 




-^ 


3] 


) 


(0 
b 













2 
■5: 

T 


>^ 




c 

< 


> 




5- 






(D 




^ 
t^ 










CO 




LJJ 






CD 





F/g. 16.7 

Electricfuse is an important component 
of all domestic circuits. Over loading can 
occur when the live wire and the neutral 
wire come onto direct contact. In such a 
situation the current in the circuit abruptly 



increases. This is called short circuiting 
. The use of an electric fuse prevents 
the electric circuit and appliance from a 
possible damage by stopping the flow of 
unduly high electric current. 



16.11. ELECTRIC POWER 

We know already that the rate of 
doing work is power. This is also the rate 
of consumption of energy. This is also 
termed as electric power. 

The power P is given by P=VI 



(or) 



p=|2 R = v^/R 



The SI unit of electric power is watt 
(W). It is the power consumed by a device 
that carries 1 A of current when operated 
at a potential difference of 1 V. Thus, 

1 W=l volt X 1 ampere =1 V A. 

The unit watt is very small. Therefore, 
in actual practice we use a much larger 
unit called "kilowatt". It is equal to 1000 
watt Since electric energy is the product 
of power and time, the unit of electric 
energy is, therefore, watt hour (Wh). One 
watt hour is the energy consumed when 
one watt of power is used for one hour. 
The commercial unit of electric energy is 
kilowatt hour (kWh), commonly known as 
'unit'. 

1 kWh = lOOOwatt x 3600second 

= 3.6x10^ watt second 

= 3.6 X 10^ joule (J) 

Example 16.7 

An electric bulb is connected to a 220 V 
generator. The current is 0.50 A. what is 
the power of the bulb? 



Solution: 

Electric generator 

voltage.V = 220 V, the current,! = 0.50 A 

The power of the bulb, 

P = VI = 220 X 0.50 = 110 W 

16.12. CHEMICAL EFFECT OF 
ELECTRIC CURRENT 



ACTIVITY 16.4 



Take out carbon rods carefully 
from two discarded cells. 

Clean their metal caps with sand 
paper. 

Wrap copper wire around the 
metal caps of the carbon rods. 

Connect these copper wires in 
series with a battery and an LED. 

Dip the carbon rods into lemon 
juice taken in a plastic or rubber 
bowl. 



Does the bulb glow? 

Does lemon juice 
electricity? 

LED 



conduct 




Fig. 16.8 



It is observed that lemon juice conduct 
electricity. 



16.13. ELECTROLYSIS- ELECTRO 
CHEMICAL CELLS 

When the current is passed through 
aqueous or molten solutions of inorganic 
acids, bases and salts, the conduction 
of electricity is always accompanied by 
chemical decomposition of the solutions 
such solutions are called electrolytes and 
the phenomenon of the conduction of 
electricity through electrolytes and chemi- 
cal decomposition is called electrolysis. 

Electro chemical cell 



Name 


: Volta 


^■IPI^H 


Born 


: 18 February 1745 




Birth place 


: Como, Italy 




Died 


: 05 March 1827 


^^^^H ■ 'a'^^^I 


Best known for 


: The Italian who built the first battery 



The cells in which the electrical en- 
ergy is derived from the chemical action 
are called electrochemical cells. 

Voltaic cell consists of two electrodes, 
one of copper and the other of zinc dipped 
in a solution of dilute sulphuric acid in a 
glass vessel. This is shown in Fig. 16.9. 



\/ 



/\ 



ffi 



'": &>l ■ 



-Dilute H.so 



2 4 



-Glass vesssi 



Fig. 16.9 



ELECTRICITY AND ENERGY 




On connecting the two electrodes ex- 
ternally, with a piece of wire, current flows 
from copper to zinc outside the cell and 
from zinc to copper inside it. The copper 
rod of the cell is the positive pole and the 
zinc rod of the cell is negative pole. The 
electrolyte is dilute sulphuric acid. 

The action of the cell is explained in 
terms of the motion of the charged ions. 
At the zinc rod, the zinc atoms get ion- 
ized and pass into solution as Zn^^ ions. 
This leaves the zinc rod with two elec- 
trons more, making it negative. At the 
same time, two hydrogen ions (2H^) are 
discharged at the copper rod, by taking 
these two electrons. This makes the cop- 
per rod positive. As long as excess elec- 
trons are available on the zinc electrode, 
this process goes on and a current flows 
continuously in external circuit. This sim- 
ple cell is thus seen as a device which 
converts chemical energy into electrical 
energy. Due to opposite charges on the 
two plates, a potential difference is set up 
between copper and zinc. Copper being 
at a higher potential than zinc, the differ- 
ence of potential between the two elec- 
trodes is 1.08 V. 

16.14. PRIMARY AND SECONDARY 
CELLS 

Primary cell 

The cells from which the electric 
energy is derived by irreversible chem- 
ical reaction are called primary cells. 

The primary cell is capable of giving an 



emf, when its constituents, two electrodes 
and a suitable electrolyte, are assembled 
together. The main primary cells are Dan- 
iel cell and Leclanche cell. These cells 
cannot be recharged. Leclanche cell is 
discussed here. 

1. Leclanche cell 

A Leclanche cell consists of a glass 
vessel which is filled with ammonium 
chloride solution. Ammonium chloride 
solution is acting as electrolyte. In it there 
stands a zinc rod and porous pot contain- 
ing a carbon rod which is packed round 
with a mixture of manganese dioxide and 
powdered carbon. Therefore the carbon 
rod forms the positive pole and the zinc 
rod the negative pole. 

Ammonium chloride, splits into 
ammonium and chloride ions. The chlo- 
ride ions migrate to the zinc rod and de- 
posit their negative charge at the zinc rod. 
Hence zinc becomes negatively charged 
and the reaction takes place in which zinc 



Carbon rod 
Zink rod 

Porous pot 

Ammonium 
chloride solution 

Mixture of carbon 
and Manganese 
dioxide 

Glass vessel 



Fig. 16.10 

is converted to zinc chloride. The ammo- 
nium ions migrate to the carbon rod and 
make it positively charged. When the car- 




bon rod and zinc rod are connected by 
a wire, the current flows from carbon to 
zinc through the wire. The e.m.f of the cell 
is about 1.5V. 

Secondary cells 

The advantage of secondary cell is 
that they are rechargeable. The chemi- 
cal reactions that take place in secondary 
cells are reversible. The active materials 
that are used up when the cell delivers 
current can be reproduced by passing 
current through the cell in opposite direc- 
tion. The chemical process of obtaining 
current from a secondary cell is called 
discharge. The process of reproducing 
active materials is called charging. One of 
the most commonly used secondary cell 
is lead acid accumulator. 

Lead-acid accumulator 

In a lead-acid accumulator, the anode 
and cathode are made of lead and lead 
dioxide respectively. The electrolyte is di- 
lute sulphuric acid. As power is discharged 




H.so, 



Glass/rubber 
container 



Fig. 16.11 

from the accumulator, both the anode and 
cathode undergoes a chemical reaction 
that progressively changes them into lead 
sulphate. When the anode and cathode 




are connected by a wire, the current flows 
from cathode to anode through the wire. 

When current is applied to a lead- 
acid accumulator, the electrochemical 
reaction is reversed. This is known as re- 
charging of the accumulator. The e.m.f of 
freshly charged cell is 2.2V. 

16.15. SOURCES OF ENERGY 

Energy comes from different forms and 
one can be converted to another. If energy 
can neither be created nor be destroyed, 
we should be able to perform endless ac- 
tivities without thinking about energy re- 
sources. But we hear so much about the 
energy crises. What is the reason? 

If we drop a plate from a height, the 
potential energy of the plate is converted 
mostly to sound energy when it hit's the 
ground. If we light a candle the chemical 
energy in the wax is converted to heat en- 
ergy and light energy on burning. 

In these examples we see that energy, 
in the usable form is dissipated to the sur- 
roundings in less usable forms. Hence 
any source of energy we use to do work 
is consumed and cannot be used again. 
We use muscular energy for carrying out 
physical work, electrical energy for run- 
ning various appliances, chemical energy 
for cooking food or running a vehicle, all 
come from a source. We should know 



ELECTRICITY AND ENERGY 




how to select the source needed for ob- 
taining energy in its usable form, and then 
only it will be a useful source. 

A good source of energy would be one 

• Which would do a large amount of 
work per unit volume of mass? 

• Be easily accessible. 

• Be easy to store and transport and 

• Perhaps most importantly be 
economical. 

16.15.1. Conventional-sources 
of energy 

1. Fossil fuels 

In ancient time's wood was the most 
common source of energy. The energy of 
flowing water and wind was also used for 
limited activities. Can you think of some 
of these uses? The exploitation of coal 
as a source of energy made the industrial 
revolution possible. Industrialisation has 
caused the global demand for energy to 
grow at a tremendous rate. The growing 
demand for energy was largely met by the 
fossil fuels, coal and petroleum. These fu- 
els were formed over millions of years ago 
and there are only limited reserves. The 
fossil fuels are non-renewable sources 
of energy. So we need to conserve them. 
If we were to continue consuming these 
sources at such alarming rates we would 
soon run out of the energy. In order to 
avoid this alternate source of energy were 
explored. 

Burning fossil fuels has other disad- 
vantages like air pollution, acid rain and 
production of green house gases. 



We will see how various sources of 
energy can be used to run the turbine and 
generate electricity in the following sec- 
tions. 

2. Thermal power plant 

Large amount of fossil fuels are burnt 
everyday in power stations to heat up 
water to produce steam which further 
runs the turbine to generate electricity. 
The transmission of electricity is more 
efficient than transporting coal or petro- 
leum over the same distance. Therefore, 
many thermal power plants are set up 
near coal or oil fields. The term thermal 
power plant is used since fuel is burnt to 
produce heat energy which is converted 
into electrical energy. 

3. Hydro power plants 

Another traditional source of energy 
was the kinetic energy of flowing water or 
the potential energy of water at a height. 
Hydro power plants convert the poten- 
tial energy of falling water into electricity. 
Since there are very few water falls which 
could be used as a source of potential en- 
ergy, hydro power plants are associated 
with dams. In the last century, a large 
number of dams were built all over the 
world. As we can see ,a quarter of our en- 
ergy requirements in India is met by hydro 
power plants. In order to produce hydro 
electricity, high-rise dams are constructed 
on the river to obstruct the flow of water 
and there by collect water in larger res- 
ervoirs. The water level rises and in this 
process the kinetic energy of flowing wa- 
ter gets transformed into potential energy. 
The water from the high level in the dam 



is carried through the pipes, to the tur- 
bine, at the bottom of the dam Fig.16.12. 
since the water in the reservoir would be 
refilled each time it rains(hydro power is 
a renewable source of energy) we would 
not have to worry about hydro electricity 
sources getting used up the way fossil fu- 
els would get finished one day. 



Power transmission cables 




Fig. 16.12 



4. Bio-mass 



We mentioned earlier that wood has 
been used as a fuel for a long time. If we 
can ensure that enough trees are planted, 
a continuous supply of fire-wood can be 
assured. You must also be familiar with 
the use of cow-dung cakes as a fuel. 
Given the large-stock published in India, 
this can also assure us a steady source of 
fuel. Since these fuels are plant and ani- 
mal products, the source of these fuels is 
set to be bio-mass. These fuels, however, 
do not produce much heat on burning and 
a lot of smoke is given out when they are 
burnt. Therefore, technological inputs to 
improve the efficiency of these fuels are 
necessary. When wood is burnt in a lim- 
ited supply of oxygen, water and volatile 
materials present in it get removed and 
charcoal is left behind as the residue. 
Charcoal burns without flames, is com- 
paratively smokeless and has higher heat 
generation efficiency. 



Similarly, cow-dung, various plant ma- 
terials like the residue after harvesting the 
crops, vegetable wastes and sewage are 
decomposed in the absence of oxygen to 
give bio-gas. Since the starting material is 
mainly cow-dung, it is popularly known as 
'go bar-gas'. The 'go bar-gas' plant struc- 
ture is shown in Fig. 16.13. 



Slurry 



Gas outlet 



Manure 

a 




Digester 



Fig 16.13 
5. Wind energy 

The kinetic energy of the wind can 
be used to do work. This energy was 
harnessed by wind mills in the past to 
do mechanical work. For example, in a 
water-lifting pump, the rotatory motion 
of windmill is utilized to lift water from a 
well. Today, wind energy is also used to 
generate electricity. A wind mill essentially 
consists of a structure similar to a large 
electric fan that is erected at some height 
on a rigid support. 

To generate electricity, the rotatory 
motion of the windmill is used to turn the 
turbine of the electric generator. The out- 
put of a single windmill is quiet small and 
cannot be used for commercial purposes. 
Therefore, a number of windmills are 
erected over a large area, which is known 
as wind energy farm. The energy output 
of each windmill in a farm is coupled to- 



ELECTRICITY AND ENERGY 




gether to get electricity on a commercial 
scale. 

Wind energy is a environment- 
friendly and efficient source of renew- 
able energy. It requires no recurring 
expenses for the production of electric- 
ity. The wind speed should be higher 




Fig. 16.14 
than 15 km per hour to maintain the re- 
quired speed of the turbine. Fig. 16.14. 

16.15.2. Non-conventional 
sources of energy 

Our life-styles are changing; we use 
machines to do more and more of our 
tasks. Therefore our demand for the en- 
ergy increases. We need to look for more 
and more sources of energy. We could 
develop the technology to use the avail- 
able sources of energy more efficiently 
and also look to new sources of energy. 
We shall now look at some of the latest 
sources of energy. 



1. Solar energy 

The sun has been radiating an enor- 
mous amount of energy at the present 



ACTIVITY 16.5 



Find out from your grand-parents 
or other elders 

(a) How did they go to school? 

(b) How did they get water for their 
daily needs when they were 
young? 

(c) What means of entertainment 
did they use? 

Compare the above answers with 
how you do these tasks now. 

Is there a difference? If yes, in 
which case more energy from 
external sources is consumed? 



rate for nearly 5 billion years and will 
continue radiating at that rate for about 
5 billion years more. Only a small part 
of solar energy reaches the outer layer 
of the earth atmosphere. Nearly half of 
it is absorbed while passing through the 
atmosphere and the rest reaches the 
earth's surface. 

A black surface absorbs more heat than 
any other surface under identical conditions. 
Solar cookers and solar water heaters use 
this property in their working. Some solar 
cookers achieve a higher temperature by 
using mirrors to focus the rays of the sun. 
solar cookers are covered with a glass plate. 

These devices are useful only at cer- 
tain times during the day. This limitation of 
using solar energy is overcome by using 
solar cells that convert solar energy into 
electricity. A large number of solar cells are 
combined in a arrangement called solar 



ACTIVITY 16.6 \ 




• Take two conical flasks and paint 
one white and the other black. 
Fill both with water. 


• Place the conical flask in direct 
sunlight for half an hour to one 
hour. 


• Touch the conical flasks. Which 
one is hotter? You could also 
measure the temperature of the 
water in the two conical flasks 
with a thermometer. 


• Can you think of ways in which 
this finding could be used in your 
daily life? 



Sun rays being 
reflected 



Glass 
vessel 




Fig. 16.15 

cell panel that can deliver enough electric- 
ity for practical use Fig. 16.16. The principal 
advantages associated with solar cells are 
that they have no moving part, require little 
maintenances. Another advantage is that 
they can be set up in remote areas in which 
laying of power transmission line may be ex- 
pensive. 



ACTIVITY 16.7 



Study the structure and working 
of a solar cooker or a solar water- 
heater, particularly with regard to 
how it is insulated and maximum 
heat absorption is ensured. 



Design and built a solar cooker 
or water-heater using low-cost 
material available and check 
what temperature are achieved 
in your solar system. 

Discuss what would be the 
advantages and limitations of 
using the solar cooker or water- 
heater. 




Fig 16.16 

16.15.3. Nuclear energy 

How is nuclear energy generated? In a 
process called nuclear fission, the nucleus 
of a heavy atom (such as uranium, pluto- 
nium or thorium), when bombarded with 
low-energy neutrons, can be split apart 
into lighter nuclei. When this is done, a 
tremendous amount of energy is released 
if the mass of the original nucleus is just a 
little more than the sum of the masses of 
the individual products. The fission of an 
atom or uranium, for example, produces 
10 million times the energy produced by 
the combustion of an atom of carbon from 



ELECTRICITY AND ENERGY 




coal. In a nuclear reactor designed for 
electric power generation sustained fis- 
sion chain reaction releases energy in a 
controlled manner and the released en- 
ergy can be used to produce steam and 
further generate electricity. 

16.15.4. Radioactivity 



Name 


: Henry Becquerel 


Born 


: 15 December 1852 


Birth place 


: Paris, France 


Died 


: 25 August 1908 


Best known for 


: Discovery of radioactivity 




The phenomenon of radioactivity was 
discovered by Henri Becquerel in 1896. 
He found that a photographic plate 
wrapped in a black paper was affected by 
certain penetrating radiations emitted by 
uranium salt. Rutherford showed later that 
the radiations from the salt were capable 
of ionizing a gas. The current produced 
due to the ions was taken as a measure 
of activity of the compound. 

A few years later Madame Marie 
Curie and her husband Pierre Curie 
discovered the highly radioactive ele- 
ments radium and polonium. The activ- 
ity of the material has been shown to be 
the result of the three different kinds of 
radiations, a, p, and y. 

The phenomenon of spontaneous 
emission of highly penetrating radia- 
tions such as a, p, and y rays by heavy 
elements having atomic number greater 
than 82 is called radioactivity and the sub- 
stances which emit these radiations are 
called radioactive elements. 

The radioactive phenomenon is spon- 
taneous and is unaffected by any external 



agent like temperature, pressure, electric 
and magnetic fields etc. 

16.15.5. Nuclear fission and 
nuclear fusion 

1. Nuclear fission 

In 1939, German scientists Otto Hahn 
and Strassman discovered that when ura- 
nium nucleus is bombarded with a neu- 
tron, it breaks up into two fragments of 
comparable masses with the release of 
energy. 

The process of breaking up of the 
nucleus of a heavier atom into two 
fragments with the release of large 
amount of energy is called nuclear fis- 
sion. The fission is accompanied of the 
release of neutrons. The fission reactions 
with U^^^ are represented as 



,,U-+,n^ 



.33Ba-+33Kr^^+3,n^ 



+ 200 Me V 



In the above example the fission reac- 
tion is taking place with the release of 3 neu- 
trons and 200 Million electron volt energy. 




L fi 



The process of fission 
Fig. 16.17 



2. Nuclear fusion 

Nuclear fusion is a process in 
wliich two or more lighter nuclei com- 
bine to form a heavier nucleus. The 

mass of the product is always less than 
the sum of the masses of the individual 
lighter nuclei. According to Einstein's 
mass energy relation E = nnc^ the dif- 
ference in mass is converted into en- 
ergy. The fusion process can be carried 
out only at a extremely high temperature 
of the order of 10^ K because, only at 
these very high temperatures the nu- 
clei are able to overcome their mutual 
repulsion. Therefore before fusion, the 
lighter nuclei must have their tempera- 
ture raised by several million degrees. 
The nuclear fusion reactions are known 
as thermo nuclear reactions. 

A suitable assembly of neutron and 
deuteron and triton is arranged at the 
sight of the explosion of the atom bomb. 
Favorable temperature initiates the fusion 
of light nuclei in an uncontrolled manner. 
This releases enormous amount of heat 
energy. This is the hydrogen bomb. 

The fusion reaction in the hydrogen 
bomb is ^H^ + ^h^ ^ ^ ^^"^ + o"^ + Energy 
Example: 16.8 

Calculate the energy produced when 
1 kg of substance is fully converted into 
energy. 



Solution: 

Energy produced, 
Mass, 
Velocity of light. 



E = mc^ 
m = 1 kg 
c = 3x10^ m s-i 
E = lx(3xiOS)2 

E =9 X 10^^ J 



16.15.6. Nuclear Reactivity 
Advantantages 

Nuclear reactivity is a measure of the de- 
parture of a reactor from criticality. It is a 
useful concept to predict how the neutron 
population of a reactor will change over 
time. 

If a reactor is exactly critical, that is, 
the neutron production is exactly equal 
to the neutron destruction, then the reac- 
tivity is zero. If the reactivity is positive, 
then the reactor is super critical. If the re- 
activity is negative, then the reactor is sub 
critical. 

16.15.7. Hazards of nuclear 
energy 

a, p and y radiations are all ioniz- 
ing radiations. These radiations cause 
a change in the structure of molecules 
in cells, disturbs the normal functioning 
of the biological system. The extent to 
which the human organism is damaged 
depends upon 

1 . The dose and the rate at which the 
radiation is given and 

2. The part of the body exposed to it. 
The damage may be either pathological 
or genetic. 

The radiation exposure is meas- 
ured by the unit called roentgen(R). One 
roentgen is defined as the quantity of ra- 
diation which produces 1.6 x 10^^ pairs of 
ion in 1 gram of air. 

Safe limit of receiving the radiation is 
about 250 milli roentgen per week. 

The following precautions are to be 
taken for those, who are working in radia- 
tion laboratories. 



ELECTRICITY AND ENERGY 




(i) Radioactive materials are kept in 
thick-walled lead container. 

(ii) Lead aprons and lead gloves are 
used while working in hazardous 
area. 

(iii) A small micro-film badge is always 
worn by the person and it is checked 
periodically for the safety limit of 
radiation. 

(iv) Nuclear devices can be operated 
using remote control system. 

(v) Clean up contamination in the work 
area promptly. 

16-15-8- SCIENCE TODAY - 
Energy from seas 

1. Tidal energy 

Due to the gravitational pull of mainly 
the moon on the spinning earth, the level 
of the water in the sea rises and falls. If you 
live near the sea or ever travel to some 
place near the sea, try and observe how 
the sea-level changes during the day. The 




Fig. 16.18 

phenomenon is called high and low tides 
and the difference in sea-levels gives us 
tidal energy. Tidal energy is harnessed by 
constructing a dam across a narrow open- 



ing to the sea. A turbine fixed at the open- 
ing of the dam converts tidal energy to 
electricity. Fig. 16.18. As you can guess, 
the locations where such dams can be 
built are limited. 

2. Wave energy 

Similarly, the kinetic energy possessed 
by huge waves near the sea-shore can be 
trapped in a similar manner that gener- 
ates electricity. The waves are generated 
by strong winds blowing across the sea. 
Wave energy would be a viable proposi- 
tion only where waves are very strong. 
A wide variety of devices has been de- 
veloped to trap wave energy for rotation 
of turbine and production of electricity. 
Fig. 16. 19 



Air back in Air out 



Generator 



Turbine 




Fig. 16.19 

3. Ocean thermal energy 

The water at the surface of the sea or 
ocean is heated by the sun while the wa- 
ter in deeper sections is relatively cooled. 
This difference in temperature is exploited 
to obtain energy in ocean-thermal-energy 
conversion plants. These plants can oper- 
ate if the temperature difference between 
the water at the surface and water at 
depths up to 2 kilometers is 293 K (20° C) 
or more . The warm surface-water is used 



to boil a volatile liquid like ammonia. The 
vapors of liquid then used to run the tur- 
bine of generator. The cooled water from 
the depth of the ocean is pumped up and 
condense vapor again to liquid. Fig. 16. 20. 

The energy potential from the sea 
(tidal energy, wave energy and ocean 
thermal energy) is quiet large, but efficient 
commercial exploitation is difficult. 



Heat 

exchangerv 

(evaporator)] 



Ammonia vapours 
Generator 



Warm 
sea water 




~. O r 



Pump 



_ Heat 
exchangET 
(condens-r) 



Liquid ammonia 

Cold sea 
water 



Discharge 



Fig. 16.20 



EVALUATION 



PART A 

1. The potential difference required 
to pass a current 0.2 A in a wire of 

resistance 20 ohm is .(100 

V, 4 V, 0.01 V, 40 V) 

2. Two electric bulbs have resistances 
in the ratio 1 : 2. If they are joined in 
series, the energy consumed in these 

are in the ratio .(1 : 2, 2 : 1 , 

4: 1, 1 : 1) 

3. Kilowatt-hour is the unit of . 

(potential difference, electric power, 
electric energy, charge) 

4. surface absorbs more heat 

than any other surface under identical 
conditions. (White, rough, black, 
yellow) 

5. The atomic number of natural 

radioactive element is . 

(greater than 82, less than 82, not 
defined, atleast 92) 

PART B 

1 . From the following statements write down 
that which does not represent ohm's law. 



a) current / potential difference = 
constant 

b) potential difference / current = 
constant 

c) current = resistance x potential 
difference 



voltmeter. 



Fill in the blanks 

a) Potential difference 
then: current . 

b) power plant : conventional source 
of energy then solar energy . 

In the list of sources of energy given 
below, some of them are wrong. List 
out the wrong ones. (Wind energy, solar 
energy, hydro electric power, nuclear 
energy, tidal energy, wave energy, geo- 
thermal energy.) 

Correct the mistakes, if any, 
in the following statements, 
a) A good source of energy would be 

one which would do a small amount 

of work per unit volume of mass, 
b) Any source of energy we use to do 

work is consumed and can be used 

again. 



ELECTRICITY AND ENERGY 




5. The schematic diagram, in which 
different components of the circuit 
are represented by the symbols 
conveniently used, is called a circuit 
diagram. What do you mean by the 
term components? 

6. Following graph was plotted between 
V and I values.What would be the 
values of V / 1 ratios when the potential 
difference is 0.8 V and 1 .2 V. 




1(A) 



7. We know that y - rays are harmful 
radiations emitted by natural radio 
active substances. 

a) Which are other radiations from 
such substances?z 

b) Tabulate the following statements 
as applicable to each of the 
above radiations 



They are electromagnetic radiation. 
They have high penetrating power. 
They are electrons. They contain 
neutrons. 

8. Draw the schematic diagram of an 
electric circuit consisting of a battery 
of two cells of 1.5V each, three 
resistance of 5 ohm, 10 ohm and 15 
ohm respectively and a plug key all 
connected in series. 

9. Fuse wire is made up of an alloy 

of which has high 

resistance and 



10. Observe the circuit given below and 
find the resistance across AB. 




11. Complete the table choosing the 
right terms from within the brackets, 
(zinc, copper, carbon, lead, leadoxide, 
aluminium.) 



+ ve electrode 


Danial cell 




- ve electrode 


Lechlechne cell 





FURTHER REFERENCE 

Books : 1. Electricity and Magnetism, by D.C Tayal Himalayam publishing 
house. 

2. Sources of energy, by C. Walker, Modern curriculam press. 


Website : 


www.reprise.com, www.wikipedia.org 



Chapter 






MAGNETIC EFFECT OF 
ELECTRIC CURRENT 
AND LIGHT 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




17. MAGNETIC EFFECT OF 
ELECTRIC CURRENT AND UGHT 




Name 


: Oersted 


Born 


: 14 August 1777 


Birth place 


: Langeland Denmark 


Died 


:9IVIarch 1851 



Best known for : The study of 

electromagnetism 



17.1. MAGNETIC FIELD AND 
MAGNETIC LINES OF 
FORCE 

We are familiar with the fact that a 
compass needle gets deflected when 
brought near a bar magnet. Why does a 
compass needle get deflected? 



ACTIVITY 17.1 



Fix a sheet of white paper on 
a drawing board using some 
adhesive material. 

Place a bar magnet in the centre 
of it. 

Sprinkle some iron fillings 
uniformly around the bar magnet 
(Fig 17.1). 

A salt-Sprinkler may be used for 
this purpose. 



Now tap the board gently. 
What do you observe? 







Fig. 17.1 

The iron fillings arrange themselves in 
a pattern as shown in Fig. 17.1. Why do 
the iron fillings arrange in such a pattern? 
What does this pattern demonstrate? The 
magnet exerts its influence in the region 
surrounding it. Therefore the iron fillings 
experience a force. The force thus exerted 
makes iron fillings to arrange in a pattern. 
The region surrounding the magnet, in 
which the force of the magnet can be 
detected, is said to have a magnetic field. 
The lines along which the iron fillings align 
themselves represent magnetic lines of 
force. 




ACTIVITY 17.2 



Take a small compass and a 
bar magnet. 

Place the magnet on a sheet of 
white paper fixed on a drawing 
board, using some adhesive 
material. 

Mark the boundary of the 
magnet. 

Place the compass near the 
north pole of the magnet. How 
does it behave? The south pole 
of the needle points towards 
the north pole of the magnet. 
The north pole of the compass 
is directed away from the north 
pole of the magnet. 

Mark the position of two ends of 
the needle. 

Now move the needle to a new 
position such that its south 
occupies the position previously 
occupied by its north pole. 

In this way, proceed step by 
step till you reach the south 
pole of the magnet as shown 

Join the points marked on the 
paper by a smooth curve. This 
curve represents a field line. 

Repeat the above procedure 
and draw as many lines as 
you can. You will get a pattern 
shown in Fig. 17. 2. These lines 
represent the magnetic field 
around the magnet. These are 
known as magnetic field lines. 

Observe the deflection of the 
compass needle as you move it 
along the field line. The deflection 
increases as the needle is moved 
towards the pole. 




Fig 17.2 




Fig 17.3 

Magnetic field is a quantity that has 
both magnitude and direction. The 
direction of the magnetic field is taken 
to be the direction in which a north pole 
of the compass needle moves inside it. 
Therefore it is taken by convention that 
the field lines emerge from the north pole 
and merge at the south pole as shown in 
Fig. 17.3. Inside the magnet, the direction 
of field lines is from its south pole to its 
north pole. Thus the magnetic field lines 
are closed curves. No two field-lines are 
found to cross each other. 

17.2. MAGNETIC FIELD DUE 
TO CURRENT CARRYING 
CONDUCTOR 

In the activity 17.3 we have seen that 
electriccurrentthroughametallicconductor 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




ACTIVITY 17.3 



Take a straight thick copper wire 
and place it between the points 
X and Y in an electric circuit, as 
shown in Fig. .17.4. The wire XY 
is kept perpendicular to the plane 
of the paper. 

Horizontally place a small 
compass near this copper wire. 
See the position of its needle. 

Pass the current through the 
circuit by inserting the key into 
the plug. 

Observe the change in the 
position of the compass needle 
and the direction of deflection. 

Replace the cell connection in 
the circuit so that the direction 
of the current in the copper wire 
changes. 

Observe the change in the 
direction of deflection of the 
needle. 




Fig 17.4 



produces a magnetic field around it. If the 
current flows in one direction (from X to 
Y), the north pole of the compass needle 
would move towards the east. If the 
current flows in opposite direction (from Y 
to X), you will see that the needle moves in 
opposite direction, that is towards the west. 
It means that the direction of magnetic field 



produced by the electric current depends 
upon the direction of flow of current. 

17.2.1. Magnetic field due to 

current carrying straight 
conductor 

What determines the pattern of the 
magnetic field generated by current 
through a conductor? Does the pattern 
depend on the shape of the conductor? 
We shall investigate this with an activity. 



ACTIVITY 17.4 



Take a battery (12 V), a variable 
resistance (rheostat), an ammeter 
(0-5A), a plug key, and a long 
straight thick copper wire. 

Insert the thick wire through the 
centre, normal to the plane of a 
rectangular cardboard. Take care 
that the cardboard is fixed and 
does not slide up or down. 

Connect the copper wire vertically 
between the points X and Y, as 
shown in Fig 17.5(a), in series 
with the battery, a plug key, 
ammeter and a rheostat. 

Sprinkle some iron fillings 
uniformly on the cardboard, (you 
may use a salt sprinkler for this 
purpose). 

Keep the variable of the rheostat 
at a fixed position and note the 
current through the ammeter. 

Close the key so that the current 
flows through the wire. Ensure 
that the copper wire placed 
between the points X and Y 
remains vertically straight. 




Gently tap the cardboard a few 
times. Observe the pattern of the 
iron fillings. You would find that 
the iron fillings align themselves 
showing a pattern of concentric 
circles around the copper wire, 
Fig 17.5(b). 

• What do these concentric circles 
represent? They represent the 
magnetic field lines. 

• How can the direction of the 
magnetic field be found? Place a 
compass at a point (say P) over 
a circle. Observe the direction of 
the needle. The direction of the 
north pole of the compass needle 
would give the direction of the 
field lines produced by the electric 
current through the straight wire 
at point P. Show the direction by 
an arrow. 

• Does the direction of magnetic 
field lines get reversed if the 
direction of current through the 
straight copper wire is reversed? 
Check it. 



Variable resistence 
f^i^A 



<s>^ 



1 




What happens to the deflection of the 
compass needle placed at a given point if 
the current in the copper wire is changed? 
We find that the deflection in the needle 
also changes. In fact, if the current is 
increased, the deflection also increases. 
It indicates that the magnitude of the 
magnetic field produced at a given point 
increases as the current through the wire, 
increases. 

What happens to the deflection of the 
needle if the compass is moved from the 
copper wire but the current through the 
wire remains the same? To see this, now 
place the compass at a farther point from 
the conducting wire. What change do you 
observe? We see that the deflection in 
the needle decreases. Thus the magnetic 
field produced by the given current in 
the conductor decreases as the distance 
from it increases. From Fig. 17.5 (b), it 
can be noticed that the concentric circles 
representing the magnetic field around 
a current-carrying straight wire become 
larger and larger as we move away from 
it. 

17.2.2. Magnetic field due to 

current carrying circular 
loop 

We have so far observed the pattern of 
the magnetic field lines produced around 
a current-carrying straight wire. Suppose 
this straight wire is bent in the form of 
a circular loop and current is passed 
through it, how would the magnetic field 
lines look like? 

We know that the magnetic field 
produced by a current- carrying straight 
wire depends inversely on the distance 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




ACTIVITY 17.5 



• Take a rectangular cardboard 
having two holes. Insert a circular 
coil having large number of turns 
through them, normal to the plane 
of the cardboard. 

• Connect the ends of the coil in 
series with a battery, a key and 
rheostat, as shown in Fig. 17. 6. 

• Sprinkle iron fillings uniformly on 
the cardboard. 

• Plug the key. 

• Tap the cardboard gently a few 
times. Note the pattern of the 
iron fillings that emerges on the 
cardboard. 



IB 



II 



Fig.17.6 



from it. Similarly at every point of a current- 
carrying circular loop, the concentric 
circles representing the magnetic field 
around it becomes larger and larger as 
we move away from the wire (Fig. 7.7). 

By the time we reach the centre of the 
circular loop, the arcs of these big circles 
would appear as straight lines. Every 
point on the wire carrying current would 
give rise to the magnetic field appearing 
as straight lines at the centre of the loop. 




Fig. 17.7 

We know that the magnetic field 
produced by a current- carrying conductor 
at a given point, depends directly on the 
current passing through it. Therefore, 
if there is a circular coil having n turns, 
the field produced is n times as large as 
produced by a single turn. This is because 
the current in each circular turn has the 
same direction, and the field due to each 
turn then just adds up. 

17-3- FORCE ON A CURRENT 
CARRYING CONDUCTOR 
IN A MAGNETIC FIELD 

We know that an electric current 
flowing through a conductor produces 
a magnetic field. The field so produced 
exerts a force on a magnet placed in the 
vicinity of a conductor. French scientist 
Andre Marie Ampere suggested that the 
magnet must also exert an equal and 
opposite force on the current carrying 
conductor. The force due to a current 
carrying conductorcan be demonstrated 
through the following activity. 




ACTIVITY 17.6 



Take a small aluminium rod AB of 
about 5 cm. using two connecting 
wires suspend it horizontally from 
a stand as shown in Fig. 17.8. 

Place a horse-shoe magnet 
in such a way that the rod lies 
between two poles with the 
magnetic field directed upwards. 
For this put the North Pole of 
the magnet vertically below and 
South Pole vertically above the 
aluminium rod. 

Connect the aluminium rod in 
series with a battery, a key and a 
rheostat. 

Now pass a current through the 
aluminium rod from end B to A. 

What do you observe? It is 
observed that the rod is displaced 
towards the left. You will notice 
that the rod gets displaced. 

Reverse the direction of current 
flowing through the rod and 
observe the direction of its 
displacement. It is now towards 
the right. 

Why does the rod get displaced? 




The displacement of the rod in the 
above activity suggests that a force is 
exerted on the current- carrying aluminium 
rod when it is placed on a magnetic field. 
It also suggests that the direction of force 
is also reversed when the direction of 
current through the conductor is reversed. 
Now change the direction of field to 
vertically downwards by interchanging the 
two poles of the magnet. It is once again 
observed that the direction of force acting 
on the current-carrying rod gets reversed. 
It shows that the direction of force on the 
conductor depends upon the direction 
of current and the direction of magnetic 
field. Experiments have shown that the 
displacement of the rod is largest when 
the direction of current is at right angles to 
the direction of magnetic field. 

17.3.1. Fleming left hand rule 

We considered that the direction of 
the current and that of the magnetic field 
perpendicular to each other and found that 
the force is perpendicular to both of them. 
The three directions can be illustrated 
through a simple rule, called Fleming's left 
hand rule. (Fig. 17.9). 



Thumb - Motion 




Field 



Current 



Force 



Current 



Fig. 17.8 



Fig. 17.9 

Stretch the thumb, fore finger and 
middle finger of your left hand such 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




that they are mutually perpendicular. 
If the forefinger points in the direction 
of magnetic field and the middle finger 
points in the direction of current, then 
the thumb will point in the direction 
of motion or the force acting on the 
conductor. 



17-4- ELECTRIC MOTOR 

An electric motor is a rotating device 
that converts electrical energy in to 
mechanical energy. Do you know how an 
electric motor works? 

An electric motor, as shown in 
Fig. 17.10, consists of a rectangular coil 
ABCD of insulated copper wire. The coil is 
placed between two poles of a magnetic 
field such that the arm AB and CD are 
perpendicular to the direction of magnetic 
field. The ends of the coil are connected 
to the two halves S^ and S^ of a split ring. 
The inner side of these halves insulated 
and attached to an axle. The external 
conducting edges of S^ and S^ touch two 
conducting stationary brushes B^ and B^, 
respectively. 




Fig. 17.9 



Current in the coil ABCD enters from the 
source battery through conducting brush 
B^ and flows back to the battery through 
brush B^. Notice that the current in arm AB 
of the coil flows from A to B. In arm CD it 
flows from C to D, that is, opposite to the 
direction of current through arm AB. On 
applying Fleming's left hand rule for the 
direction of force on a current-carrying 
conductor in a magnetic field. We find 
that the force acting on arm AB pushes it 
downwards while the force acting on arm 
CD pushes it upwards. Thus the coil and 
the axle, mounted free to turn about an 
axis, rotate anti-clockwise. At half rotation 
S2 makes contact with the brush B^ and S^ 
with brush B^. Therefore the current in the 
coil gets reversed and flows along the path 
DCBA. A device that reverses the direction 
of flow of current through a circuit is called 
a commutator. In electric motors, the split 
ring acts as a commutator. The reversal 
of current also reverses the direction of 
force acting on the two arms AB and CD. 
Thus the arm AB of the coil that was earlier 
pushed down is now pushed up and the 
arm CD previously pushed up is now 
pushed down. Therefore the coil and the 
axle rotate half a turn more in the same 
direction. The reversing of the current is 
repeated at each half rotation, giving rise 
to a continuous rotation of the coil and to 
the axle. 

The commercial motors use (i) an 
electro magnet in place of permanent 
magnet; (ii) large number of turns of the 
conducting wire in the current-carrying 
coil, and (iii) a soft iron core on which the 
coil is wound . The soft iron core, on which 
the coil is wound, plus the coils, is called 
an armature. This enhances the power of 
the motor. 




17-5- ELECTROMAGNETIC 
INDUCTION 

Faraday in 1831 discovered that an 
electro motive force is produced in a 
circuit whenever the magnetic flux linked 
with a coil changes. He showed that emf 
is generated in a conductor when ever 
there is a relative motion between the 
conductor and a magnetic field. Then emf 
produced in this way is called an induced 
emf and the phenomenon is known as 
electro magnetic induction. The induced 
emf will cause a current to flow through 
the conductor. Such a current is known 
as induced current .Faraday made an 
important break through by discovering 
how a magnet can be used to generate 
electric currents. 

17.5.1. Faraday's Experiments 

We know that when a current-carrying 
conductor is placed in a magnetic field, it 
experiences a force. This force causes the 
conductor to move. Now let us imagine a 
situation in which a conductor is moving 
inside a magnetic field or a magnetic field 
is changing around a fixed conductor. 
What will happen? To observe this effect, 
let us perform the following activity. 



ACTIVITY 17.7 




Fig. 17. 11 



Take a coil of wire AB having a 
large number of turns. 



• Connect the ends of the coil 
to a galvanometer as shown 
in Fig. 17. 11 

• Take a strong bar magnet and 
move its north pole towards 
the end B of the coil. Do 
you find any change in the 
galvanometer reading? 

• There is a momentary 
deflection in the needle of the 
galvanometer, say to the right. 
This indicates the presence of 
a current in the coil AB. The 
deflection becomes zero, the 
moment the motion of the 
magnet stops. 

• Now withdraw the north pole 
of the magnet away from the 
coil. Now the galvanometer 
is deflected toward the left, 
showing that the current is 
now setup in the direction 
opposite to the first. 

• Place the magnet stationary 
at the point near to the coil, 
keeping its north pole toward 
the end B of the coil. We 
see that the galvanometer 
needle deflects towards the 
right when the coil is moved 
towards the north pole of the 
magnet. Similarly the needle 
moves toward left when the 
coil is moved away. 

• When the coil is kept stationary 
with respect to the magnet, the 
deflection of the galvanometer 
drops to zero. What do you 
conclude from this activity? 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




You can also check that if you have 
moved South Pole of the magnet towards 
the end B of the coil, the deflections in 
the galvanometer would just be opposite 
to the previous case. When the coil and 
the magnet are both stationary, there is 
no deflection in the galvanometer. It is 
thus clear that motion of a magnet with 
respect to the coil produces an induced 
electromotive force, which sets up an 
induced electric current in the circuit. 

Let us now perform a different activity in 
which the moving magnet is replaced by a 
current-carrying coil and the current in the 
coil can be varied. 



ACTIVITY 17.8 



• Two different coils of copper 
wire having large number of 
turns (say 50 and 100 turns 
respectively). Insert them over a 
non conducting cylindrical roll as 
shown in Fig. 17. 12. 

• Connect the coil -1 having large 
number of turns, in series with 
a battery and a plug key. Also 
connect the other coil -2 with a 
galvanameter assam. 

•##Plug in the key. Observe the 
galvanameter. Is there a deflection 
in its needle?. You will observe that 
the needle of the galvanameter 
instantly jumps to one side and 
just as quickly returns to zero, 
indicating a momentary current in 
coil -2. 

• Disconnect coil-1 from the 
battery. You will observe that the 
needle momentarily moves, but 
to the opposit side. It means that. 



Now the current flows in the 
opposite direction in coil -2. 




Fig. 17.12 



In this activity we observe that as soon 
as the current in coil-1 reaches either a 
steady value or zero, the galvanometer 
in coil-2 shows no deflection. From these 
observations we conclude that a potential 
difference is induced in coil-2 when ever 
the current through the coil-1 is changing. 
Coil-1 is called the primary coil and coil-2 
is called the secondary coil. As the current 
in the first coil changes, the magnetic field 
associated with it also changes. Thus the 
magnetic field lines around the secondary 
coil also change. Hence the change in 
magnetic field lines associated with the 
secondary coil is the cause of induced 
electric current in it. The direction of 
the induced current can be found using 
Fleming's right hand rule. 

Stretch the thumb, forefinger and 
middle finger of right hand so that they 
are perpendicular to each other. If the 
forefinger indicates the direction of the 
magnetic field and the thumb shows the 
direction of motion of conductor, then the 
middle finger will show the direction of 
induced current. 




17.6. ELECTRIC GENERATOR 

The phenomenon of electro magnetic 
induction is employed to produce large 
currents for use in homes and industry. In 
an electric generator, mechanical energy 
is used to rotate a conductor in a magnetic 
field to produce electricity. 

An electric generator, as shown 
in Fig. 17. 13a, consists of rotating 
rectangular coil ABCD placed between 
the two poles of a permanent magnet. 
The two ends of this coil are connected to 
the two rings S^ and S^. The inner sides of 
these rings are made insulated. The two 
conducting stationary brushes B^ and B^ 
are kept pressed separately on the rings 
S^ and S2 respectively. The two rings S^ 
and S2 are internally attached to an axle. 
The axle may be mechanically rotated 
from outside to rotate the coil inside the 
magnetic field. Outer ends of the two 
brushes are connected to the external 
circuit. 

When the axle attached to the two rings 
is rotated such that the arm AB moves up, 
the arm CD moves down in the magnetic 
field produced by the permanent magnet. 
Let us say the coil ABCD is rotated 
clockwise. By applying Fleming's right- 
hand rule the induced currents are setup 
in these arms along the directions AB 
and CD. Thus an induced current flows 
in the direction ABCD. If there are large 
numbers of turns in the coil, the current 
generated in each turn adds up to give a 
large current through the coil. This means 
that the current in the external circuit flows 
from B2 to B^. 

After half a rotation, arm CD starts 
moving up and AB moving down. As 



a result, the directions of the induced 
currents in both the arms change, 
giving rise to the net induced current in 
the direction DCBA. The current in the 
external circuit now flows from B^ to B^. 
Thus after every half rotation the polarity 
of the current in the respective arms 
changes. Such a current which changes 
direction after equal intervals of time, is 
called an alternating current (AC). This 
device is called an AC generator. 



B OC 





D.C Generator 
b 
Fig 17.13 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




To get a direct current (DC), a split- 
ring type commutator must be used witii 
this arrangement, Fig. 17. 13b, one brush 
is at all times in contact with the arm 
moving up in the field, while the other is in 
contact with the arm moving down. Thus 
a unidirectional current is produced. The 
generator is thus called a DC generator. 

An important advantage of AC over DC 
is that electric power can be transmitted 
over long distances without much loss of 
energy. 

17.7. LIGHT 

We see a variety of objects in the world 
around us. However we are unable to see 
anything in a dark room. On lighting up 
the room things becomes visible. What 
makes things visible? During the day the 
sunlight helps us to see objects. An object 
reflects light that falls on it. This reflected 
light when received by our eyes, enables 
us to see things. 

There are a number of common 
wonderful phenomena associated with 
light. In this chapter, we shall study the 
phenomena of reflection and refraction of 
light using the straight-line propagation of 
light. 

Reflection of light 

A highly polished surface, such as a 
mirror, reflects most of the light falling on 
it. You are already familiar with the laws of 
reflection of light. Let us recall these laws. 

(i) The angle of incidence is equal to the 

angle of reflection, and 
(ii) The incident ray, the normal to the 

mirror at the point of incidence and 

the reflected ray, all lie in the same 

plane. 



These laws of reflection are applicable 
to all types of reflecting surfaces including 
spherical surfaces. 

Spherical mirrors 



ACTIVITY 17.9 



• Take a perfect hemispherical 
spoon. Try to view your face in its 
curved surface. 

• Do you get the image? Is it larger 
or smaller? 

• Move the spoon slowly away from 
your face. Observe the image. 
How does it change? 

• Reverse the spoon and repeat 
the activity. How does the image 
look like now? 

• Compare the characteristics of 
the images on the two surfaces. 



The curved surface of a shining spoon could 
be considered as a curved mirror. The most 
commonly used type of curved mirror is the 
spherical mirror. The reflecting surface of a 
spherical mirror may be curved inwards or 
outwards. A spherical mirror wliose 
reflecting surface is curved inwards is 
called a concave mirror A spherical 
mirror whose reflecting surface is 
curved outwards is called a convex 
mirror The schematic representation of 
these mirrors is shown in Fig. 17.14. 



(a) concave mirror 



(b) convex mirror 



Fig 17.14 




You may now understand that the 
surface of the spoon curved inwards can be 
approximated to a concave mirror and the 
surface of the spoon bulged outwards can 
be approximated to a convex mirror. 

Before we move further on spherical 
mirrors, we need to recognise and understand 
the meaning of a few terms. These terms 
are commonly used in discussions about 
spherical mirrors. 

The centre of the reflecting surface of a 
spherical mirror is a point, called the pole. It 
is represented by the letter P. 

The reflecting surface of a spherical 
mirror forms a part of a sphere. This sphere 
has a centre. This point is called the centre 
of curvature of the spherical mirror. It is 
represented by the letter C. 

The radius of the sphere of which the 
reflecting surface of a spherical mirror forms 
a part, is called the radius of curvature of the 
mirror. It is represented by the letter R. 

Imagine a straight line passing through 
the pole and the centre of curvature of 
a spherical mirror. This line is called the 
principle axis. 



ACTIVITY 17.10 



• Hold a concave mirror in your hand 
and direct its reflecting surface 
towards the sun. 

• Direct the light reflected by the 
mirror on to a sheet of paper held 
close to the mirror. 

• Move the sheet of paper back and 
forth gradually until you find on the 
paper sheet a bright, sharp spot of 
light. 

• Hold the mirror and the paper in the 
same position for a few minutes. 
What do you observe? Why? 



Let us understand important terms 
related to mirrors, through above activity. 

The paper at first begins to burn 
producing smoke. It may even catch fire. 
Why does it burn? The light from the sun 
is converged at a point, as a sharp, bright 
spot by the mirror. In fact, this spot of 
light is the image of the sun on the sheet 
of paper. This point is the focus of the 
concave mirror. The heat produced due 
to the concentration of the sunlight ignites 
the paper. The distance of the image 
from the position of the mirror gives the 
approximate focal length of the mirror. 
Observe Fig. 17. 15(a) closely 





fu\ At Infinity 

Fig. 17.15 

A number of rays parallel to the principal 
axis are falling on a concave mirror. 
Observe the reflected rays. They are all 
meeting at a point on the principal axis of 
the mirror. This point is called the principal 
focus of the concave mirror. Similarly 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




observe Fig. 17.15(b). How are the rays 
parallel to the principal axis reflected by a 
convex mirror? The reflected rays appear 
to come from a point on the principal axis. 
This point is called the principal focus of 
the convex mirror. The principal focus is 
represented by the letter R 

The distance between the pole and 
the principal focus of a spherical mirror 
is called the focal length. It is represented 
by the letter f. 

The diameter of the reflecting surface of 
spherical mirror is called its aperture. In fig 
17.15, distance MN represents the aperture. 
In our discussion we shall consider only 
such spherical mirrors whose aperture is 
much smaller than its radius of curvature. 

Is there any relationship between the 
radius of curvature R, and focal length f, of 
a spherical mirror? For spherical mirrors of 
small apertures the radius of curvature is 
found to be equal to twice the focal length. 
WeputthisasR = 2f. 

17.7.1 Reflection of light by spherical 
mirror 

The reflection of light by a spherical mirror 
takes place according to certain definite 
rules as follows. 




(i) A ray parallel to the principal axis, 
after reflection, will pass through principal 
focus in case of a concave mirror or appear 
to diverge from the principal focus in case 
of a convex mirror. This is illustrated in Fig. 
17.16(a) and (b). 




(b) 



Fig. 17.16 

(ii) A ray passing through the principal 
focus of a concave mirror or a ray directed 
towards the principal focus of a convex 
mirror, after reflection, will emerge parallel 
to the principal axis. This is illustrated in 
Fig.17.17(a)and(b). 






(b) 
(iii) A ray passing through the centre of 
curvature of a concave mirror or directed 
in the direction of the centre of curvature 
of a convex mirror, after reflection, is 
reflected back along the same path. This 
is illustrated in Fig. 17. 18 (a) and (b). 




(a) 




Image formation by concave mirror 

How about the images formed by 
spherical mirrors? How can we locate 
the image formed by a concave mirror 
for different positions of the object? 
Are the images real or virtual? Are the 
images enlarged, diminished or have 
the same size? 

The nature, position and size of the 
image formed by a concave mirror 
depend on the position of the object in 
relation to point P, F and C. The image 
formed is real for some positions of the 
object. It is found to be a virtual image 
for a certain other position. The image 
is either magnified, reduced or has the 
same size, depending on the position of 
the object. 

We can study the formation of image 
by spherical mirrors by drawing ray 
diagrams. To construct the ray diagrams, 
it is more convenient to consider only 
two rays. These rays are so chosen that 
it is easy to know their directions after 
reflection from the mirror. You may take 
any two of the rays mentioned in the 
previous section for locating the image. 
The intersections of the two reflected rays 
give the position of image of the point 
object. This is illustrated in the Fig.17.19. 

Uses of concave mirror 

Concave mirrors are commonly used in 
torches, search-lights and vehicles head 
lights to get powerful parallel beams of 
light. They are used as shaving mirrors to 
see a lager image of the face. The dentists 
use concave mirrors to see large images 
of the teeth of patients. Large concave 
mirrors are used to concentrate sun light 
to produce heat in solar furnaces. 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




B 

At Infinity 




-|V| 




At Infinity (e) / (f) 

Fig 17.19 
A summary of these observations is given in Table: 17.1. 




Position of 
^ the Object 


Position of the 
image 


Relative size of 
the image 


Nature of the 
image 


At infinity 


At focus F^ 


Highly dimin- 
ished, point-sized 


Real and inverted 


Beyond 2F^ 


Between F2and 2F2 


Diminished 


Real and inverted 


At2F^ 


At2F2 


Same size 


Real and inverted 


Between F^&2F^ 


Beyond 2F2 


Enlarged 


Real and inverted 


At focus F^ 


At infinity 


Infinitely large or 
highly enlarged 


Real and inverted 


Between focus 
F^ and optical 
centre O 


On same side of the 
lens as the object 


Enlarged 


Virtual and erect 



Table 17.1 




Image formation by a convex mirror 

We consider two positions of tine object for studying tine image formed by a convex 
mirror. First is when the object is at infinity and the second position is when the object 
is at a finite distance from the mirror. The ray diagrams for the formation of image by a 
convex mirror for these two positions of the object are shown in Fig 17.20(a) and (b), 
respectively. 

M 




B 

At Infinity 



Fig. 17.20 
A summary of these observations is given in Table: 17. 2 



Position of the 
object 


Position of the 
image 


Relative size of 
the image 


Nature of the 
image 


At infinity 


At focus F^ 


Highly dimin- 
ished, point-sized 


Virtual and erect 


Between infinity 
and optical centre 
O of the lens 


Between focus F^ 
and optical centre 
O 


Diminished 


Virtual and erect 



Table 17.2 

You have studied the image formation by a concave mirror and a convex mirror, 
which of these mirrors will give the full image of a large object? Let us explore through 
an activity. 



ACTIVITY 17.11 



Observe the image of a distant tree in a concave mirror. 

Could you see a full length image? 

Repeat this Activity with a convex mirror. Did the mirror show full length 



image of the object? 

Explain your observations with reason. 



You can see a full length image of a tree in a small convex mirror. 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




Uses of convex mirrors 

Convex mirrors are commonly used 
as rear-view mirrors in vehicles. These 
mirrors are fitted on the sides of the 
vehicle, enabling the driver to see traffic 
behind him/her to facilitate safe driving. 
Convex mirrors are preferred because 
they always give an erect image. Also 
they have a wider field of view as they 
are curved outwards. 

Sign convention for reflection by 
spherical mirrors 

While dealing with the reflection of 
light by spherical mirrors, we shall follow 
a set of sign conventions called the New 
Cartesian Sign Convention. In this 
convention, the pole (P) of the mirror is 
taken as the origin. The principal axis of 
the mirror is taken as the X axis (X'X) of 
the coordinate system. The conventions 
are as follows. 

(i) The object is always placed to the 
left of the mirror. 

(ii) All distances parallel to the principal 
axis are measured from the pole of 
the mirror. 

(iii) All the distances measured to the 
right of the origin (along +X-axis) 
are taken as positive while those 
measured to the left of the origin 
(along -X-axis) are taken as negative 

(iv) Distances measured perpendicular 
to and above the principal axis (along 
+Y-axis) are taken as positive. 

(v) Distances measured perpendicular 
to and below the principal axis (along 
-Y-axis) are taken as negative. 



The New Cartesian Sign Convention 
described above is illustrated in Fig. 1 7.21 . 



Object on the left 

Direction of 



Height 

Upwards 

{+ve} 



M 




Fig. 17.21 

These sign conventions are applied to 
obtain the mirror formula 

Mirror formula 

in a spherical mirror, the distance of 
the object from its pole is called the object 
distance (u). The distance of the image 
from the pole of the mirror is called the 
image distance (v). You already know that 
the distance of the principal focus from the 
pole is called the focal length (f). There 
is a relationship between these three 
quantities given by the mirror formula 
which is expressed as 

llv + 1/1/ = II f 

This formula is valid in all situations for 
all spherical mirrors for all positions of the 
object. You must use the New Cartesian 
Sign convention while substituting 
numerical values for u, v, f, and R in the 
mirror formula for solving problems. 

Example: 17.1 

A convex mirror used for rear-view on 
an automobile has a radius of curvature 
of 3 m. If a bus is located at 5 m from this 




mirror, find the position and nature of the 
image. 

Solution: 

Radius of curvature, R = +3.00 m 

Object distance u = - 5.00 m 

Image distance v = ? 

Focal length , 

f = R/2 = + 3.00 m/2 = 1.5 m 

We know, 

111 

V u f 



or, 



111 
V f u 



111 



1.5 -5.00 1.5 5.00 
5.00 +1.50 6.50 



7.50 



7.50 



7.50 

V= = 1.15 m 

6.50 

The image is 1.15 m at the back of the 
mirror. The image is virtual. 

17.7.2. Refraction of light 

Light seems to travel along straight- 
line paths in a transparent medium. What 
happens when light enters from one 
transparent medium to another? Does 
it still move along a straight-line path or 
change its direction? We shall recall some 
of our day-to-day experiences. 

You might have observed that the 
bottom of a tank or a pond containing 



water appears to be raised. Similarly, 
when a thick glass slab is placed over 
some printed matter, the letters appear 
raised when viewed through the glass 
slab. Why does it happen? Have you seen 
a pencil partially immersed in water in a 
glass tumbler? It appears to be displaced 
at the interface of air and water. You might 
have observed that a lemon kept in water 
in a glass tumbler appears to be bigger 
than its actual size, when viewed from 
the sides. How can you account such 
experiences? 

Let us consider the case of the 
apparent displacement of the pencil, partly 
immersed in water. The light reaching you 
from the portion of the pencil inside water 
seems to come from a different direction, 
compared to the part above water. This 
makes the pencil appear to be displaced 
at the interface. For similar reasons, the 
letters appear to be raised, when seen 
through a glass slab placed over it. 

Does a pencil appear to be displaced 
to the same extent, if instead of water, we 
use liquids like kerosene or turpentine? 
Will the letters appear to rise to the 
same height if we replace a glass slab 
with a transparent plastic slab? You 
will find that the extent of the effect is 
different for different pair of media. These 
observations indicate that light does not 
travel in the same direction in all media. It 
appears thatwhen traveling obliquely from 
one medium to another, the direction of 
propagation of light in the second medium 
changes. This phenomenon is known as 
refraction of light. Let us understand this 
phenomenon further by doing an activity. 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




ACTIVITY 17.12 



• Place a coin at the bottom of a 
bucket filled with water. 

• With your eye to a side above 
water, try to pick up the coin 
in one go. Did you succeed in 
picking up the coin? 

• Repeat the Activity. Why did you 
not succeed in doing it in one go? 

• Ask your friends to do this. 
Compare your experience with 
theirs. 



The apparent position of the coin as 
seen through water differ from its actual 
position . 

Laws of refraction 

Refraction of light is due to change 
in the speed of light as it enters from 
one transparent medium to another. 
Experiments show that refraction of light 
occurs according to certain laws. The 
following are the laws of refraction of light. 

(i) The incident ray, the refracted ray 
and the normal to the interface of 
two transparent media at the point 
of incidence, all lie in the same 
plane, 

(ii) The ratio of sine of angle of 
incidence to the sine of angle of 
refraction is a constant, for the 
light of a given colour and for the 
given pair of media. This law is also 
known as Snell's law of refraction. 
If / is the angle of incidence and r is 
the angle of refraction, then. 

Sin / /sin r = constant 



This constant value is called the 
refractive index of the second medium 
with respect to the first. 

17.7.3 Refractive index 

We know that a ray of light travels 
obliquely from one transparent medium 
into another will change its direction in the 
second medium. The extent of the change 
in direction that takes place in a given 
pair of media is expressed in terms of the 
refractive index of the second medium 
with respect to the first medium. 

The refractive index can be linked 
to the relative speed of propagation of 
light in different media. Light propagates 
with different speeds in different media. 
It travels the fastest in vacuum with the 
highest speed of 3 x 10^ m s"^. Its speed 
reduces considerably in glass. 

Consider a ray of light traveling from 
medium 1 into medium 2 as in Fig. 17.22. 

Let i,r be the angle of incidence and 
angle of refraction. 

N 

Medium 1 
(Air) 





\ 
l\ 




IVIedium 2 




1 \ 


k 


( Glass) 


N 




\ 





Fig. 17.22 

The refractive index of the second 
medium with respect to the first 
|Li = Sin //sin r 



|Ll = 



Speed of light in air 



Speed of light in medium 




17.7.4 Refraction by spherical 
lenses 

Spherical lenses 

You might have seen people using 
spectacles for reading. The watchmakers 
use a small magnifying glass to see tiny 
parts. Have you ever touched the surface 
of a magnifying glass with your hand? Is it 
plane surface or curved? Is it thicker in the 
middle or at the edges? The glasses used 
in spectacles and that by watchmaker are 
examples of lenses. What is a lens? How 
does it bend light rays? Let us discuss in 
this section. 

A transparent material bound by two 
surfaces, of which one or both surfaces 
are spherical, forms a lens. This means 
that a lens is bound by at least one 
spherical surface. In such spherical 
lenses, the other surface would be plane. 
A lens may have two spherical surfaces, 
bulging outwards. Such a lens is called 
a double convex lens. It is simply called 
a convex lens. It is thicker at the middle 
as compared to the edges. Convex lens 
converges light rays. Hence it is called 
converging lens. Similarly, a double 
concave lens is bounded by two spherical 
surfaces, curved inwards. It is thicker at 
the edges than at the middle. Such lenses 
diverge light rays and are called diverging 
lenses. A double concave lens is simply 
called a concave lens. 

Let us understand the meaning of a 
few terms which are commonly used in 
discussions about spherical lenses. A 
lens has two spherical surfaces. Each of 
these surfaces forms a part of a sphere. 
The centers of these spheres are called 
centres of curvature of the lens. The 



centre of curvature of a lens is usually 
represented by the letter C. Since there 
are two centre's of curvature, we may 
represent them as C^ and C2. 

An imaginary straight line passing 
through the two centres of the curvature 
of a lens is called its principal axis. 

The central point of a lens is called its 
optical centre. It is represented by the 
letter O. A ray of light through the optical 
centre of a lens passes without suffering 
any deviation. 

The effective diameter of the circular 
outline of a spherical lens is called its 
aperture. Lenses whose aperture is 
much less than its radius of curvature 
are called thin lenses with small aperture. 
What happens when parallel rays of light 
are incident on a lens? 



ACTIVITY 17.13 



• CAUTION: Do not look at the sun 
directly or through a lens while 
doing this Activity or otherwise. 
You may damage your eyes if 
you do so. 

• Hold a convex lens in your hand. 
Direct it towards the sun. 

• Focus the light from the sun on 
a sheet of paper. Obtain a sharp 
bright image of the sun. 

• Hold the paper and the lens in 
the same position for a while. 
Keep observing the paper. What 
happened? Why? 



The light from the sun constitutes 
parallel rays. These rays were converged 
by the lens as a sharp bright spot. 
This is the real image of the sun. The 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




concentration of the sun light at this spot principal foci. They are represented by F^ 

generated heat. This caused the paper to 

burn. 



Observe Fig. 17.23(a) carefully. 







Fig.l) 

M 

A 


^.23(a) 








\ 


X' 


Ci 




\ s 






2F 


Fi 


— 1 


-^i^^^^ 


2F2 




\j 




\ 



Several rays of light parallel to the 
principal axis are falling on a convex lens. 
These rays after refraction from the lens 
are converging to a point on the principal 
axis. This point is called the principal 
focus of the lens. 

Observe Fig. 17.23(b) carefully, 

Fig. 17.23(b) 









^ •-• 


2Fi 


Fi "■•• 

j 



and F^. 

The distance of the principal focus 
from the optical centre of a lens is called 
its focal length. The letter f is used to 
represent the focal length. 

17.7.5 Image formation by lenses 

We can represent image formation by 
lenses using ray diagrams. Ray diagrams 
will also help us to study the nature, 
position and relative size of the image 
formed by the lenses. For drawing ray 
diagrams in lenses, we consider any two 
of the following rays. 

(i) A ray of light from the object, parallel 
to the principal axis, after refraction 
from a convex lens, passes through the 
principal focus on the other side of the 
lens, as shown in Fig. 17.24(a). In case 
of a concave lens, the ray appears to 
diverge from the principal focus located 
on the same side of the lens, as shown in 
Fig. 17.24(b) 



Fi 




Several rays of light parallel to the 
principal axis are falling on a concave 
lens. These rays after refraction from the 
lens, are appearing to diverge from a point 
on the principal axis. This point is called 
the principal focus of the concave lens. 

If you pass parallel rays from the 
opposite surface of the lens, you will get 
another principal focus on the opposite 
side. Letter F is usually used to represent 
principal focus. However, a lens has two 





\ -f 




.'►* 


•"V 




• ■ Fi 


A 


F2 




(b) 
Fig. 17.24 






(ii) A ray of light passing through 
a principal focus after refraction from 
a convex lens will emerge parallel to 
the principal axis. This is shown in Fig 
17.25(a). A ray of light appearing to 
meet at the principal focus of a concave 
lens, after refraction, will emerge parallel 
to the principal axis. This is shown in 
Fig. 17.25(b). 




(b) 
Fig. 17.25 
(iii) A ray of light passing through 
the optical centre of a lens will emerge 
without any deviation. This is illustrated in 
Fig 17.26(a) and (b). 




Sign convention for spherical lenses: 

All measurements are taken from the 
optical centre of the lens. According to the 
convention, the focal length of a convex 
lens is positive and that of a concave lens 
is negative. We must take care to apply 
appropriate signs for the values of u, v, f, 
object height h and image height h\ 

17.7.6 Lens formula 

This formula gives the relation between 
object-distance (a), image-distance (v) 
and the focal length {f). The lens formula 
is expressed as 

1 



1 1 



V 



u 



f 



The lens formula given above is 
general and is valid in all situations for 
any spherical lenses. 

Example: 17.2 

A concave lens has focal length of 15 
cm. At what distance should the object 
from the lens be placed so that it forms an 
image 10 cm from the lens? 

Solution: 

u = ? 



v = 


-10 cm, 


f = - 15 cm, 


X. 


X = 


1- 


V 


u 


f Or, 




1 


1 1 




u 


V f 




1 


1 1 




u 


-10 -15 




1 


-3 + 2 -1 



30 



30 



u = -30 cm 

Thus, the object distance is 30 cm. 



Fig. 17.26 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




The ray diagrams for the image formation in a convex lens for a few positions of the 
object are shown in Fig. 17.27. 



m 







A 


j-^_^ 




: r 


^ 


c, 







:^-^F2 


2F1 


F1 


J 


\^ 


-^2 


: u 


"^ 






I 






A 


M 






B 


r^v,^^^^ 




\F, 2F. 


2F 


"i Fi 


i* 'x,,^^ 


Ac' 


Bt 


C 


1 











Fig. 17.27 
A summary of these observations is given in Table 17.3. 



Positionon of the 
object 


Position of the 
image 


Relative size of 
the image 


Nature of the 
image 


At infinity 


At focus F 


Highly dimin- 
ished, point-sized 


Real and inverted 


Beyond 2F 


Between F and 2F 


Diminished 


Real and inverted 


At2F 


At2F 


Same size 


Real and inverted 


Between F and 2F 


Beyond 2F 


Enlarged 


Real and inverted 


At focus F 


At infinity 


Infinitely large or 
highly enlarged 


Real and inverted 


Between focus F 
and optical centre 
O 


On the Same 
side of the lens 
as the object 


Enlarged 


Virtual and erect 



Table 17.3 




The ray diagrams for the image formation in a concave lens for various positions of 
the object are shown in Fig. 17.28. 





2F B 



N ^^ FT" 

(a) (b) 

Fig. 17.28 
A summary of these observations is given in Table. 17.4. 



Position of 


Position of the 


Relative size of the 


Nature of the 


the objecob- 


image 


image 


image 


ject 








At infinity 


At focus F 


Highly diminished, 
point-sized 


Virtual and erect 


Between infin- 


Between focus 


Diminished 


Virtual and erect 


ity and optical 


F and optical 






center O of the 


center O 






lens 









Table 17.4 



Magnification 

The magnification produced by a 
lens is defied as ttie ratio of ttie tieigtit 
of ttie image to ttie tieigtit of ttie object 

It is represented by the letter m. If h 
is the height of the object and h' is the 
height of the image given by the lens, 
then the magnification produced by the 
lens is given by. 



m = 



Height of the image (h') v 
Height of the object (h) u 



Example: 17.3 

An object is placed at a distance of 30 
cm from a concave lens of focal length 15 
cm. An erect and virtual image is formed 
at a distance of 10 cm from the lens. 
Calculate the magnification. 

Solution: 

Object distance, u = -30 cm 
Image distance, v = -10 cm 

Magnification, m = v/u 

-10 cm 1 
m= = — = + 0.33 

-30 cm 3 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




17.7.7. Power of lens 

The degree of convergence or 

divergence of light rays achieved by a 

lens is expressed in terms of its power. 

The power of a lens is defined as 

the reciprocal of its focal length. It is 

represented by the letter P. The power P 

of a lens of focal length f is given by 

1 
P = — 
f 

The SI unit of power of a lens is 
'dioptre'. It is denoted by the letter D. 
If f is expressed in meter, then, power is 
expressed in dioptres. Thus 1 dioptre is 
the power of a lens whose focal length 
is 1 meter. The power of a convex lens 
is positive and that of a concave lens is 
negative. 

Example: 17.4 

The focal length of a concave lens is 
2m. Calculate the power of the lens. 

Solution: 

Focal length of concave lens, f = - 2 m 
Power of the lens, 

1 



P = 



P = 



f 
1 

-2m 



p = - 0.5 dioptre 

17.7.8. Refraction of light through a 
prism 

Consider a triangular glass prism. It has 
two triangular bases and three rectangular 
lateral surfaces. These surfaces are 
inclined to each other. The angle between 
its lateral faces is called the angle of the 
prism. Let us now do an activity to study 



the refraction of light through a triangular 
glass prism. 



ACTIVITY 17.14 



Fix a sheet of white paper on a 
drawing board using drawing pins. 

Place a glass prism on it in such 
a way that it rests on its triangular 
base. Trace the out line of the 
prism using a pencil. 

Draw a straight line PE inclined 
to one of the refracting surfaces, 
sayAB, of the prism. 

Fix two pins, say at points P and 
Q, on the line PE as shown in 
Fig 17.29 

Look for the images of the pins, 
fixed at P and Q, through the 
other face AC. 

Fix two more pins, at points R 
and S, such that the pins at R and S 
lie on the same straight line. 

Remove the pins and the glass 
prism. 

The line PE meets the boundary 
of the prism at point E (see 
Fig 17.29). Similarly, join and 
produce the points R and S. Let 
these lines meet the boundary of 
the prism at E and F, respectively. 
Join E and F. 

Draw perpendicular to the 
refracting surfaces AB and AC 
of the prism at points E and F, 
respectively. 

Mark the angle of incidence (Zi), 
the angle of refraction (Zr) and 
the angle of emergence (Ze) as 
shown in Fig 17.29. 




M 



i 


/V •■■•■• "^^ 


V\ ■••■■■■■' 


^/ 




\ 



PE - Incident ray 
EF - Refracted ray 
FS - Emergent ray 
/LK - Angle of the Prism 



/i. \ - Angle of incident 
Z_\ - Angle of refraction 
^e - Angle of emergence 
^ D - Angle of deviation 



F\g.l7.29 

Here PE is the incident ray. EF is the 
refracted ray. FS is the emergent ray. You 
may note that a ray of light is entering from 
air to glass at the first surface AB. The 
light ray on refraction has bent towards 
the normal. At the second surface AC, 
the light ray has entered from glass to 
air. Hence it has bent away from normal. 
Compare the angle of incidence and angle 
of refraction at each refracting surface of 
the prism. The peculiar shape of prism 
makes the emergent ray bent at an angle 
to the direction of the incident ray. This 
angle Zr is called the angle of refraction. 
In this case ZD is the angle of deviation. 
Mark the angle of deviation in the above 
activity and measure it. 

17.7.9. Dispersion of white light 
by a glass prism 

You must have seen and appreciated 
the spectacular colours in a rainbow. 
How could the white light of the sun 
give us various colours of the rainbow? 

The prism has probably split the incident 
white light into a band of colours. Note 
the colours that appear at the two ends of 
the colour band. What is the sequence of 



ACTIVITY 17.15 



• Take a thick sheet of cardboard 
and make a small hole in its 
middle. 

• Allow sunlight to fall on the 
narrow slit. This gives a narrow 
beam of white light. 

• Now, take a glass prism and 
allow the light from the slit to fall 
on one of its faces. 

• Turn the prism slowly until the 
light that comes out of it appear 
on a near by screen. 

• What do you observe? You will 
find a beautiful band of colours. 

• Why does this happen? 



colours that you see on the screen? The 
various colours seen are Violet, Indigo, 
Blue, Green, Yellow, Orange and Red. As 
shown in Fig. 17.30. 




White light^ 
beam 



F\Q. 17.30 

The acronym VIBGYOR will help you 
to remember the sequence of colours. 

The band of the coloured component of a 
light beam is called its spectrum. You might 
not be able to see all the colours separately. 
Yet something makes each colour distinct 
from the other. The splitting of light into its 
component colours is called dispersion. 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




You have seen that white light 
is dispersed into its seven-colour 
components by a prism. Why do we get 
these colours? Different colours of light 
bend through different angles with respect 
to the incident ray as they pass through 
the prism. The red light bends the least 
while the violet the most. Thus the rays of 
each colour emerge along different paths 
and thus become distinct. It is the band of 
distinct colours that we see in a spectrum. 

17.7.10. Atmospheric refraction 

You might have observed the apparent 
random wavering or flickering of objects 
seen through a turbulent stream of hot air 
rising above a fire. The air just above the 
fire becomes hotter than the air further up. 
The hotter air is lighter (less dense) than the 
cooler air above it, and has a refractive index 
slightly less than that of the cooler air. Since 
the physical conditions of the refracting 
medium (air) are not stationary, the apparent 
position of the object, as seen through the 
hot air fluctuates. This wavering is thus an 
effect of atmospheric refraction (refraction 
of light by the earth's atmosphere) on a 
small scale in our local environment. The 
twinkling of stars is a similar phenomenon 
on a much larger scale. 

17.7.11. Human eye 

The human eye is one of the most 
valuable and sensitive sense organs. It 
enables us to see the wonderful worlds 
and colours around us. Of all our sense 
organs, the human eye is the most 
significant one as it enables us to see the 
beautiful, colorful world around us. 

The human eye is like a camera. Its 
lens system forms an image on a light- 
sensitive screen called the retina. Light 



enters the eye through the thin membrane 
called the cornea. It forms the transparent 
bulge on the front surface of the eye ball 
as shown in Fig. 17.31. 



Crystalline lens 



Aqueous 
humour 



Ciliary muscles 

Retina 




Cornea 



Optic nerve 



Vitreous 
humour 



Fig 17.31 

The eye ball is approximately spherical 
in shape with a diameter of about 2.3cm. 
Most of the refraction for the light rays 
entering the eye occurs at the outer 
surface of the cornea. The crystalline lens 
merely provides the finer adjustment of 
focal length required to focus objects at 
different distances on the retina. We find 
a structure called iris behind the cornea. 
Iris is a dark muscular diaphragm that 
controls the pupil. The pupil regulates 
and controls the amount of light entering 
the eye. The eye lens forms an inverted 
real image of the object on the retina. 
The retina is a delicate membrane having 
enormous number of ligtit-sensitive 
cells. The light sensitive cells get 
activated upon illumination and generate 
electrical signals. These signals are 
sent to the brain via the optic nerves. 
The brain interprets these signals, and 
finally, processes the information so that 
we perceive objects as they are. 




Defects of vision and rectification 

There are mainly three common 
refractive defects of vision. These are 
(i) Myopia or near - sightedness.(ii) 
Hypermetropia or far-sightedness, and 
(iii) Presbyopia. These defects can be 
corrected by the use of suitable spherical 
lenses. 

(a) Myopia 

Myopia is also l<nown as near- 
sightedness. A person with myopia 
can see near by objects clearly but 
cannot see the distant objects distinctly. 
A person with this defect has the far 
point nearer than infinity. Such a person 
may see clearly up to a distance of a 
few meters. In a myopic eye, the image 
of a distant object is formed in front of 
the retina [Fig. 17.32(a)] and not at the 
retina itself. 



This defect may arise due to (i) 
excessive curvature of the eye lens, or 
(ii) elongation of the eyeball. This defect 
can be corrected by using a concave lens 
of suitable power. This is illustrated in 
Fig. 17. 32(c). A concave lens of suitable 
power will bring the image back on to the 
retina and thus the defect is corrected. 

(b) Hypermetropia 

Hypermetropia is also known 
as far-sightedness. A person with 
hypermetropia can see distant objects 
clearly but cannot see near by objects 
distinctly. The near point, for the person, 
is further away from the normal near point 
(25 cm). Such a person has to keep a 
reading material such beyond 25cm from 
the eye for comfortable reading. This is 
because the light rays from a close by 
object are focused at a point behind the 
retina as shown in Fig. 17.33 (b) 




(b) myopia eye 




(c) Correction of myopia 
Fig. 17.32 




(c) correction of hypemetropia eye 



Fig. 17.33 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




This defect either because (i) the focal 
length of the eye lens is too long or (ii) the 
eyeball has become too small. This defect 
can be corrected by using a convex lens 
of appropriate power. This is illustrated 
in Fig. 17.33(c). Eye- glasses with 
converging lenses provide the additional 
focusing power required for forming the 
image on the retina. 

(c) Presbyopia 

The power of accommodation of the 
eye usually decreases with ageing. For 
most people, the near point gradually 
recedes away. They find it difficult 
to see near by objects comfortably 
and distinctly without corrective 
eye - glasses. This defect is called 
Presbyopia. It arises due to the gradual 
weakening of the ciliary muscles and 
diminishing flexibility of the eye lens. 
Sometimes, a person may suffer from 
both myopia and hypermetropia. Such 
people often require by-focal lenses. 
A common type of by-focal lenses 
consists of both concave and convex 
lenses. The upper portion consists of a 
concave lens. It facilitates near vision. 
These days, it is possible to correct the 
refractive defects with contact lenses. 

17.12- Science today - Hubble 
space telescope (H.S.T) 

Hubble telescope is a space telescope 
that was carried into orbit by a space 
shuttle in April 1990. It is named 
after the American astronomer Edwin 
Hubble. It becomes a most popular 
research tool for astronomy. The H.S.T 
is collaboration between NASA and the 
European Space Agency, and is one of 
NASA's great observatories. 



Hubble is the only telescope ever 
designed to be serviced in space by 
astronauts. The H.S.T design with two 
hyperbolic mirrors is known for good 
imaging performance over a wide field of 
view. During the launch scientist found 
that the main mirror had been ground 
incorrectly, which severely affect the 
telescopes capabilities. After a servicing 
mission in 1993, the telescope was 
restored to its intended quality. Four 
servicing missions where performed from 
1993-2002. But the fifth was completed in 
2009. The telescope is now expected to 
function until at least 2014. 




Fig. 17.34 

Hubble's orbit outside the distortion 
of earth's atmosphere allows it to take 
extremely sharp images with almost no 
background light. Hubble's Ultra Deep 
Field image is the most detailed visible- 
light image ever made of the universe's 
most distant object. Hubble Deep field 
and Hubble ultra Deep field images 
reveals that galaxies are billions of light 
years away. 

Many Hubble observations accurately 
measure the rate at which the universe 
is expanding. It constrain the value of 




Nubble's constant and estimates the age 
of the Universe. 

Nubble's images of planets were crucial 
in studying the dynamics of the collision of 
a comet with Jupiter, an event believed to 
occur once every few centuries. 



Nubble's observations found that 
black holes are common to the centers 
of all galaxies. 

The astronomers used the telescope 
to observe distant supernovae. 



EVALUATION 



PART A 

1. The magnification produced by a mirror is 
1/3, then the type of mirror is 

(concave, convex, plane) 

2. An electric current through a metallic conductor 
produces around it. 

(heat, light, magnetic field, mechanical force) 

3. The field of view is maximum for 

(plane mirror, concave mirror, convex mirror) 

4. An object is placed 25 cm from a convex 
lens whose focal length is 10 cm. The image 

distance is .(50 cm, 16.66 cm, 6.66 

cm, 10 cm) 

PARTB 

1 . From the following statement write down that 
which is applicable to a commutator. 

a) galvanometer uses commutator for 
dead beat 

b) transformer uses commutator to step up 
voltage 

c) mototr uses commutator to reverse the 
current 

2. Fill in the blanks 

a) For a motor : a permanent magnet, then 
commercial motor : 

b) Focal length of a lens; meter, then for 
power of a lens 

3. Correct the mistakes, if any, in the following 
statements. 

a) Magnetic field is a quantity that has 
magnitude only. 



b) The magnetic field lines emerge from the 
south pole and merge at the north pole. 

4. The ray diagram shown below is introduced 
to show how a concave mirror forms an 
immage of an object. 

a) identify the mistake and draw the correct 
ray diagram. 

b) Write the justifications for your corrections. 

M 




5. In traffic signals 



colour light is 



used to stop vechides because it is having 
wave length. 

6. Considering this write down the names of the 
parts in human eye. 

a) Dark muscular diaphragm that controls 
the pupil. 

b) The screen at where the image is formed 
by eye lens. 

7. You know that myopia is a common refractive 
defects of vision. Person with this defect 
can see only nearby objects clearly. Using 
concave lens of suitable power this defect is 
corrected. 

a) mention other two types of defects like 
this. 



MAGNETIC EFFECT OF ELECTRIC CURRENT AND LIGHT 




b) explain how can we correct it. 

8. (a) Which of the compass needle orientations 
in the following diagram might correctly 
describe the magnet's field at that point? 
b 




^v 




n 





(b) To an astronaut sky appears dark instead 
of blue. Give the reason. 

PART-C A 





/ .-4dV ...... .■•■■■ 


. 





1 . (a) Label the following in the given diagram 
given below. 



a) Incident ray b) Refracted ray 

c) Emergent ray d)Angle of refraction 

e) Angle of deviation f) Angle of emergence 

1. (b)The retractive index of diamond is 2.42. 
What is the meaning of this statement in 
relation to speed of light? 




2. a) Re draw the above diagram, 
b) This diagram represents 



c) Label the parts of the diagram. 

d) Write the principle of the name of the 
device denoted by this diagram. 



FURTHER REFERENCE 

Books: 1 . Fundamentals of optics 

D.R. Khanna and H.R. Gulati R.Chand & Co 

2. Magnetism Joy Frisch - Schnoll published by Creative Eduction. 

3. Advanced physics Keith Gibbs Cambridge University press 

Website: www.physics about.com 

www.opticalsres.com 
www.newdn.com. 



SYLLABUS 



1. Applied Biology 


Heredity and Evolution :- Heredity -Variations-Evolution-Speciation- 
Human evolution-Evolution tree-Genetic engineering-Bio technology 
and cloning-Stem cell-Organ culture-Microbial production-Biosensor 
- Bio chips-Science today - Gene therapy 


2. Health and 
Hygiene 


Immune System:- Health and its significance-Diseases and causes- 
Diseases caused by microbes and prevention-Modes of transmission- 
Immunization-Treatment and prevention-Biotechnology in Medicine- 
H IV and Prevention 


3. My Body 


Structure & Function of the Human Body - Organ System:- 

Nervous system-Endocrine system-Cell division-Stages of Meiosis- 
Heredity 


4. World of Plants 


Reproduction in Plants:-Modes of reproduction - vegetative, 
asexual and sexual reproduction in plants-Pollination-Fertilization- 
Fruits and seeds formation-Seed dispersal 


5. World of Animals 


A Representative Study of Mammals- Morphology-Habitats- 
Adaptations-Basic Physiological Functions. -Circulatory system in 
man-Excretory system in man. -Relationship of structure to functions- 
Animal Behaviour - Behaviour (social, reproductive, parental care) 
-Some case studies from researchers(animals behavior) 


6. Life Process 


Life Processes:- Definition-Types of nutrition and human digestive 
system-Respiration -Transportation in plants-water and minerals and 
animals - blood circulation-Excretion in plants and animals-Nervous 
system-Coordination in plants-Movement due to growth-Hormones 
in animals 


7. Environmental 
Science - Ecology 


Conservation of Environment:- Bio degradable and non bio 
degradable wastes-Water management-Wild life sanctuaries- 
Balance in Ecosystem-Coal and petroleum-Green chemistry-Science 
today - Towards a global village 


8. Environmental 
Science - 
Resource use and 
Management 


Waste Water Management:- Journey of water-Sewage -Treatment 
-Domestic practices -Sanitation and diseases-Alternate arrangement 
for sewage disposal -Sanitation in public places-Energy Management- 
Energy audit (home, school)- Renewable sources (solar, hydrogen, 
wind)- Non-renewable sources — (coal, petroleum, natural gas)- Bio- 
fuels-generation & use-Energy Conservation & How we can help. 


9. Matter 


Solutions:- Solute and Solvent-Types of Solutions-Solubility-Factors 
affecting - Solubility-Problems 


10. Atomic Structure 


Atoms and Molecules:- Modern atomictheory- Avogadro Hypothesis- 
Atomicity-Relation between vapour density and molecular mass of a 
gas- Difference between-Atom and Molecules-Relative Atomic Mass- 
Relative Molecular mass-Mole Concepts- Mole- Definition-Problems 
based on mole concept 




Exploring 
11. Chemical Changes 
and Formulation 


Chemical Reactions:- Types of chemical reactions -Rate of chemical 
reaction-Factors influencing the rate of the chemical reaction-Acids- 
Classification of acids- Chemical properties of acids-Uses of acids-Bases- 
Classification of bases-Chemical properties of bases- uses of bases- 
Identification of acids and bases-pH scale-pH paper-Importance of pH in 
everyday life-Salts- Classification of salts-Uses of salts 


12 

Exploring 

Chemical Families 


Periodic Classification of Elements:- Modern periodic law-Modern 
periodic table-Characteristics of modern periodic table-Metallurgy -Intro- 
duction-Terminologies in metallurgy-Differences between Minerals and 
Ores-Occurrence of metals- Metallurgy of Al, Cu and Fe- Metallurgy of 
Aluminium-Metallurgy of Copper- Metallurgy of iron- Alloys- Methods of 
making alloys-Copper Aluminium and Iron alloys-Corros ion -Method s 
of preventing corrosion 


13. Exploring the World 


Carbon and its Compounds:- Introduction-Compounds of carbon-Mod- 
ern definition of organic chemistry-Bonding in carbon and its compounds- 
Allotropy- Physical nature of carbon and its compounds- Chemical- prop- 
erties of carbon compounds-Homologous series-Hydrocarbons and their 
types -Functional groups- Classification of organic compound based on 
functional group-Ethanol-Ethanoic acid 


. . Matter and 

Measurement 


Measuring Instruments:- Screw Gauge-Measuring long-Distances -As- 
tronomical distance, light year 


. J- Forces and 
Movement 


Laws of Motion and Gravitation-Balanced and imbalanced forces-First 
law of motion-Inertia and mass-Momentum-Second aw of motion-F=ma- 
Third law of motion-Conservation of momentum and proof-Moment of 
force and couple-Gravitation Newton's law of gravitation -Mass- Weight- 
Acceleration due to gravity-Mass of Earth-Science Today- Chandrayan, 
Cryogenic Techniques and Manned Space Station 


16. Exploring Energy 


Electricity and Energy:- Electric current and circuit-Electric potential and 
potential difference-Circuit diagram-Ohm's law-Resistance of a conduc- 
tor-System of resistors -Heating effect of electric current-Joules law of 
heating-Role of fuse-Domestic electric circuits-Electric power-Chemical 
effect of electric current-Electrolysis electro chemical cells-Primary and 
Secondary cells-Sources of Energy-Conventional sources of energy- 
Non- conventional source of energy- Nuclear energy-Radioactivity- 
Nuclear fission and nuclear fusion-Nuclear reactivity advantages- 
Hazards of nuclear energy-Science today- Energy from seas. 


^^ Exploring 
Phenomena 


Magnetic Effect of Electric Current and Light :-Magnetic field and 
magnetic lines of force-Magnetic field due to current carrying conductor- 
Magnetic field due to current carrying Straight conductor- Magnetic field 
due to current carrying Circular loop-Force on a current carrying conductor 
in a magnetic field-Fleming left hand rule -Electric motor-Electromagnetic 
induction- Faraday's experiments-Electric generator -Light-Reflection of 
light by Spherical mirrors - image formation and Mirror Formula - Refrac- 
tion - Laws of refraction-Refractive index-Refraction by spherical lens- 
es- Image formation by lenses-Lens formula and magnification-Power 
of lens-Refraction of light through a prism-Dispersion-By a glass prism- 
Atmospheric refraction- Human eye -Defects and rectification-Science 
today -Hubble space telescope 


18. Technology 


Practical and Projects 



Design of Question Paper - X Std Science (Theory) 
Time: 2% Hours Max. Marl<s: 75 

The weightage of marks allotted for the design of question paper shall be as under: 



A. Weightage to Learning Outcome 



SI.No 


Categories 


Mark 


PERCENTAGE 


1 


Knowledge 


17 


15 


2 


Understanding 


52 


45 


3 


Application 


35 


30 


4 


Skill 


11 


10 




Total 


115 


100 



Note: (1) Total Marks is 115 inclusive of choice. (2) While preparing the question paper, there may be 
variations in weightage to the extent from 2 % to 5 %. 

B. Weightage given to various types of question 



S.No 


Types of Questions 


Marks 
for Each 
Question 


Total 

No. of 

Questions 


No. of Questions 
to be answered 


Total 
Marks 


1 


Section A 

Objective Type (OT) 


1 


15 


15 


15x 1=15 


2 


Section B 

Short Answer (SA) 


2 


30* 


20 


20x2 = 40 


3 


Section C 

Long Answer (LA)* 


5 


8 


4 


4 X 5 = 20 




Total 53 


39 


75 



Each Question may be split into 2 or 3 sub-divisions carrying 1 , 2 or 3 marks. But the questions shall 
be from each area (Botany, Zoology, Chemistry, Physics). Choices will be internal (Either - or) 

*Short Answer split up 



Sl.No. 


Very Short Answer 
Type of Questions 


To be 
asked 


1 


To Matcli 


3 


2 


To spot the error / mistake in the given statements 


3 


3 


Reason and Assertion 


3 


4 


To Raise questions 


3 


5 


To label the parts in the given diagram 


3 


6 


To copy a diagram & to identify /mark the parts 


3 


7 


To calculate the required value(Problem solving) 


3 


8 


To fill up the blanks (from the given pair of answers) 


3 


9 


To interpret what happens in the given situations 


3 


10 


To find the odd one out 


3 




Total Number of Questions given 


30 




Total Number of Questions to be answered 


20 



u 



C. Weightage given to the higher order of questions 




SI.No 


Estimated higher order of questions 


% Percentage 


1 


Easy 


50 


2 


Average 


40 


3 


Difficult 


10 



D. Weightage to Content Unit 



Units 






No. of Questions 


Total 
Marks 




OT 


SA 


LA 




1. Heredity and Evolution 


o 

o 
o 

N 
■D 

c 
c 

05 
O 

cn 


1(1) 


1(2) 


1(5) 


23 


8 


2. Immune System 


1(1) 


1(2) 


1(5) 


8 


3. Structure & Function of the Human 
Body - Organ System 


- 


3(2) 


- 


6 


4. Reproduction in Plants 


1(1) 


1(2) 


1(5) 


8 


5. A representative Study of Mam- 
mals 


- 


3(2) 


- 


6 


6. Life Processes 


1(1) 


1(2) 




3 


7. Conservation of Environment 


1(1) 


1(2) 


1(5) 


8 


8. Waste Water Management 


- 


3(2) 


- 


6 


9. Solutions 


-1— » 

CO 

E 

CD 

O 


1(1) 


2(2) 


- 


15 


5 


10. Atoms and Molecules 


- 


1(2) 


1(5) 


7 


11. Chemical Reaction 


1(1) 


2(2) 




5 


12. Periodic Classification of Elements 


2(1) 


2(2) 




6 


13. Carbon and its Compounds 


1(1) 


1(2) 


1(5) 


8 


14. Measurements 










15 


- 


15. Laws of Motion and Gravitation 


(/) 
o 

CO 
CL 


1(1) 


2(2) 


1(5) 


10 


16. Electricity and Energy 


2(1) 


3(2) 




8 


17. Magnetic Effect of Electric Current 
and Light 


2(1) 


3(2) 


1(5) 


13 


Total Number of Questions 

given 




15(15) 


30(60) 


8(40) 


53 


115 


Total Number of Questions to be an- 
swered 




15(15) 


20(40) 


4(20) 


39 


75 



Indicates the marks 



a. 

Q. 

LU 

D 

_l 

CD 



Total 
Marks 


CO 


00 


to 


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to 


00 


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to 


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00 


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SCIENCE PRACTICALS 



S.No ^^^^^^H Content 



Biological Science (Zoology & Botany) 

1 To find out the presence of starch in the given food samples of A and B 
by using iodine solution. 

2 To find out the rate of heart beat of human beings by using stethoscope 
under normal physical conditions. 

To find out the body temperature by using clinical thermometer and to 
compare with surrounding temperature. 

To calculate is the Body Mass Index (BMI) of a person, by using the BM I 
formula and to compare the value with BMI chart. 

To dissect and display the androecium and gynoecium of any locally 
available flowers. 

6 To classify the fruits,separating the pericarps and writing the edible parts. 

7 To identify the structure of ovule. 

8 To prove the anaerbic respiration (Fermentation). 

Physical Science (Chemistry & Physics) 

9 To find the pH of a given solution using pH paper. 

10 To identify the presence of acids and bases in a given solution. 

11 Preparation of true solution, colloidal solution and suspension. 

12 To predict whether the reaction exothermic or endothermic. 

13 Screw cauge-measuring small dimensions. 

14 Resistance of a coil of wire, 

15 To map of magnetic field of a bar magnet when its north pole pointing 
north of the earth. 

16. Focal length of a convex lens by distance object method. 

Record the findings directly in tine table provided. 



1 



Zoology 



Ex. No. 1 



Date 



To find out the presence of starch in the given food samples of A and B 
by using Iodine solution. 

Aim: 

To find out the presence of starch in the given food samples of A and 
B by using iodine solution. 

Requirements: 

Test tubes, Iodine solution. 
Procedure: 

Take 1 ml of foood sample A and B in separate test tubes. 
Add one drop of Iodine solution in bothe the test tubes. 
Observe the colour change and record. 

Indication : Appearence of dark blue colour indicates the presence of 
starch. 



Table: 



SI.No 


Food Sample 


Observation 


Presence / Absence of Starch 


1 


A 






2 


B 







Result: 



The food sannple_ 



contains starch. 



1 



Ex. No. 2 



Date 



To find out the rate of heart beat of human beings by using stethoscope 
under normal physical conditions. 



Aim: 

To find out the rate of heart beat of a person by using stetheoscope. 
Requirements: 

Stethoscope, stop watch. 

Procedure: 

Use the stethoscope and hear Lubb and Dubb sound which make up 
a heart beat. 



Count the number of heart beats per minute and record. 



Table: 



SI. No 


Persons 


No. of heart beat per minute 


1 


A 




2 






3 






4 






5 








Average : 





Inference: 



Under normal conditions the average human heart beat is found 
to be per minute. 



Ex. No. 3 



Date 



To find out the body temperature by using clinical thermometer and to 
compare with surrounding temperature. 

Aim: 

To find out the body temperature of human being using clinical thermometer. 
Requirement: 

Clinical thermometer, lab thermometer 
Procedure: 

Find out the room temperature by using lab thermometer. 

Clean the Clinical thermometer in dilute dettol soaked cotton. 

Shake the clinical thermometer at least four times. 

Keep the mercury bulb of the clinical thermometer at the arm pit in boys or 
elbow in girls for a minute and record the temperature. 

Repeat the same outside the room and record your findings for atleast three 
of your friends. 

Table: 



S.No 


Test 


Body 
Temperature °F 


Room 
Temperature °C 


C=F-32 X 5/ 9 


1 


Inside the room 
Outside the room 








2 


Inside the room 
Outside the room 








3 


Inside the room 
Outside the room 









Inference: 

Under normal conditions the body temperature of human beings is 
°F, °C. 

The body temperature of human beings remains the or same/ varies irrespective of 
surroundings. 



1 



Ex. No. 4 



Date 



To calculate the Body Mass Index (BMI) of a person, by using the BMI 
formula and comparing the value with BMI chart. 

Aim: 

To calculate the BMI of any one of your classmates by using the BMI formula. 
Requirements: 

Weighing machine, measuring tape. 

Procedure: 

Find out the weight in kg of your calssmate by using weighing machine. 

Find out the height of the same person and convert into meter^ 

By using the formula 

weight in kg 
BMI = 

height in m^ 

Find out the BMI and record. 
Note: 

BMI 19-25 is normal , 26 and above is obese, below 19 is lean. 
Table: 



SI. No 


Persons 


weight 
in Wg 


Height in meter 


Height in meter^ 


BMI 


1 












2 












3 













Inference: 



The BMI of my classmate Selvan/Selvi 
so he/she is normal / obese / lean. 



IS 



and 



Botany 



Ex. No. 5 



Date 



To dissect and display the androecium and gynoecium of any locally 
available flowers. 

To dissect and display the androecium and gynoecium of any locally 
available flowers. 

Androecium 

1) Androecium is the male reproductive part. 

2) It has two parts, the filament and anther. 

3) Pollen grains develop inside the anther. 

Gynoecium 

1) Gynoecium is the female reproductive part. 

2) It has three parts, the ovary style and stigma. 

3) Ovules are seen inside the ovary. 

Separate the Androecium and Gynoecium of a given flower and paste in a 
separate sheet. Record your observations with regard to number of stamen 
shape of anther and shape of stigma in the given table. 



Sl.no 


Name of the flower 


Androecium 


Gynoecium 


1. 
2. 
3. 
4. 
5. 









1 



Ex. No. 6 



Date 



To classify the fruits. Separate the pericarps and write the edible parts and 
fill in the blanks 



Simple fleshy fruits 
Berry - Tomato 

1) The pericarp is divided into. 



.and 



2) The mesocarp and endocarp remain. 

3) The edible part in tomato is 

Berry - Banana 

1) The pericarp is divided into 

2) The epicarp is and the mesocarp is. 

3) The edible part in banana is 

Hesperidium - Orange/Lemon. 



and 



1) The pericarp is differentiated into 

2) The outer glandular skin is 

3) A middle thin whitish layer is 

4) An inner membranous part is 



layers. 



5) The juicy hairs or out growths are 

Pepo - Cucumber/ivy gourd (Kovai) 

1) The pericarp is and_ 

2) The mesocarp is 

3) The edible part is 

Drupe - Mango 

1) The number of seeds in mango is 

2) Pericarp is differentiated into epicarp,. 
and 



3) Epicarp is s. 
endocarp is 



, mesocarp is 
.in nature. 



.and 



4) Edible part of the mango is 

Drupe - Coconut 

1) The pericarp is differentiated into 



.and 



2) The epicarp is thick, the mesocarp is 
endocarp is hard. 

3) The endosperm seen inside the 



and the 



is edible. 



Classify the given fruits, record your observations in the given table. 



SI. No. 


Type of fruit of 
fruit 


Nature of pericarp 


Edible part 


1. 
2. 
3. 









Ex. No. 7 

To identify the structure of ovule. 



Date 



The given slide kept for identification is L.S. of ovule 

The characteristics of ovule : 

1) The ovule has layers of walls called as integuments. 

2) Inner to the integuments, is present. 

3) The embryo sac has , and 



Observe the given slide and record your observations in the table 



SI. No 



Observation 



1. 
2. 
3. 



Ex. No. 8 Date : 

To prove the anaerbic respiration (fermentation). 
Aim: 

To prove the anaerobic respiration(fermentation) 
Materials required: 

Test tube, sugar solution, yeast. 
Procedure: 

Sugar solution in a test tube is taken. A little quantity of yeast is added. 

The tube is placed in a warm place-sunlight. 
Record your observations and inference in the table given below : 



Observation 


Inference 







Results: The alcohol smell indicates that the sugar is converted into alchohol 
in the fermentation process 



1 



Chemistry 

Ex. No. 9 Date : 

To find the pH of a given solution using plH paper. 
Aim: 

To find the pH of the given solution using pH paper. 

Materials and Apparatus required: 

Test tubes, test tube stand, test tube holder, pH paper, dil. HCI, dil. NaOH, 
lemon juice, water, baking soda solution, vinegar etc. 

Procedure: 

Take about 10 ml of the given samples in different test tubes and label 
them as A, B, C, D, E and F. Dip the pH paper into the test tubes and 
compare the colour of pH paper with the colour chart of pH reference. 
Note the approximate value of pH. 

Table: 



Test tubes 


Sample 


pH paper 


Nature of solution 


Colour 
produced 


Approximate 
pH 


Acidic/Basic/ 
Neutral 


A 










B 










C 










D 










E 










F 











Ex. No. 10 Date : 

To identify acids and bases 

Aim 

To identify the presence of an acid or a base in a given sample. 

Materials and apparatus required : 

Test tubes, test tube stand, glass rod, litmus paper (botli red and blue), 
acids, bases, plienolplithalein, metliyl orange solution. 

Note: 

• All acidic solutions are colourless in plienolplithalein, pink in metliyl 

orange and turn blue litmus paper to red. 

• All basic solutions are pinl< in phenolphthalein, straw yellow in metliyl 

orange and turn red litmus paper to blue. 



S.No 


Experiment 


Observation 
(Colour change) 


1 

Inference 

(Acid/base) 


1 


Tal<e 5 ml of the test 
solution in a test tube, 
add phenolphthalein in 
drops to this content. 






2 


Take 5 ml of the test 
solution in a test tube 
and add methyl orange 
in drops. 






3 


Take 10 ml of the test 
solution in a 
test tube and dip litmus 
paper into the test tube. 







1 



Ex. No. 11 Date : 

Preparation of true solution, colloidal solution and suspension 
Aim : 

To prepare true solution, colloidal solution and suspension 
Materials and apparatus required : 

Beakers, common salt, table sugar, starch, chalk powder, 
sand, egg albumin. 
Procedure: Take 20ml of water in three different beakers and label them as 

A, B & C. Add common salt in A, starch in B, and chalk power in C. 

Stir the contents of three different beakers gently. Record your 

observations. 



Beaker 


Observation 


Inference 


A. 






B. 






C. 







Note : 

i. If the particles do not settle down at the bottom and pass through 
the filter paper easily the solution is said to be a true solution. 

ii. If the particles do not settle down but they form turbid solution 
then the solution is said to be a colloidal solution. 

iii. If the particles settle down to form sediments leaving behind 
residue on the filter paper then the solution is said to be a 
suspension. 

Result : True solution is in beaker 



Colloidal solution is in beaker 
Suspension is in beaker 



Ex. No. 12 



Date 



To predict whether the reaction is exothermic or endothermic. 
Aim. 

To predict whether a reaction is exothernnic or endothermic using 
the given chemicals 

Materials and apparatus required 

Test tubes, test tube stand, water, glass rod, sodium hydroxide 
(pellets),ammonium chloride etc. 

Note: 

• Exothermic reaction evolves heat 

• Endothermic reaction absorbs heat 



S.No 


Experiment 


Observation( hot/cold) 


Inference 
(exo/endo) 


1 


Take water in a test 
tube. Add sodium 
hydroxide pellets one by 
one followed by stirring. 
Touch the test tube and 
note the observation. 






2 


Take water in a test tube. 
Add ammonium chloride 
salt and stir well .Touch 
the test tube and note 
the observation. 







1 



PHYSICS 

Ex. No. 13 Date : 

SCREW GAUGE - Measuring small dimensions of the object 

Aim: 

To find the radius of the given wire. 
Apparatus required : 

Screw gauge, a uniform thin metal wire. 
Formula : 

Radius of the wire r = 612, d - diameter of the wire. 



S2 



rt 



SI Hallow Cylindrical tube 



Milled Head (H) 



U-Shaped Frame 




pitch scale 

Head Scale 
Index line 



Safety device (D) 
(Ratchat) 





o 



-^ 



95 



1 




Procedure : 



The least count of the screw gauge is found .Zero error of the screw gauge is 
found in the following way. The plane surface of the screw and the opposite 



plane stud on the frame are brought in to contact. If zero of head scale 
coincides with the pitch scale axis, there is no zero error. 

If the zero of the head scale lies below the pitch scale axis, the zero error is 
positive. If the n th division of the head scale coincides with the pitch scale axis 

ZE = + (n X LC ) 

Then the zero correction ZC = - (n x LC ) 

If the zero of the head scale lies above the pitch scale axis, the zero error is 
negative. If the n th division of the head scale coincides with the pitch scale axis 

ZE = -(100-n)xLC 

Then the zero correction ZC = + (100 - n) x LC 

Place the wire between two studs. Rotate the head until the wire is held firmly 
but not tightly . Note the pitch scale reading(PSR) and the head scale division 
which coincides with the pitch scale axis (HSC). The diameter of the wire is 
given by PSR + (H.S.C x LC) + ZC. Repeat the experiment for different portions 
of the wire. Tabulate the readings. The average of the last column readings 
gives the diameter(d) of the wire. The value d/2 gives the radius of the wire. 



Table: 



Z-E = 



Z,C = 



S.No 


P.S.R (mm) 


H.S.C 


H.S.C X 
L.C 


Total reading 
P.S.R +(H.S.C xL.C) ± Z.C (mm) 


1 










2 










3 
















Mean = 





The radius of given wire r = d/2 
Result : 

The radius of the given wire = 



mm 



1 



Ex. No. 14 



Date 



RESISTANCE OF A WIRE 



Aim 



To determine the resistance of the given wire . 

Apparatus required 

A battery(2 V), ammeter(1.5 A), voltmeter(1.5 V), key, rheostat, experimental 
wire(1 Q or 2 Q) and connecting wires. 



Formula 



Resistance of the wire R = 



V 
I 



V is the potential difference across the wire. 
I is the strength of the current through the experimental wire. 



Circuit diagram: 

-Hi 



K 

■<•>■ 






+ - 



^ 



Bt 

K 

Rh 

A 

R 

V 



Battery 

Key 

Rheostat 

Ammeter 

Resistance (unknown) 

Voltmeter 




Procedure 

Connect the battery eliminator, ammeter the given wire, rheostat and key in 
series. The voltmeter is connected in parallel connection across the given wire. 
The circuit is closed and the rheostat is adjusted such that a constant current 
flows through the given coil of wire. The current is noted as T from the ammeter 
and the potential difference across the wire V is noted from the voltmeter. The 
value V/l gives the resistance of the wire. The experiment is repeated for different 
values of the current. 

V 
The average value of — gives the resistance of the wire R. 

Tabulation 



Trial No 


Ammeter reading 
1 (ampere) 


Voltmeter reading 
V (volt) 


Resistance 
R = V/l (ohm) 


1 








2 








3 








4 








5 









Mean R = 



Result 

Resistance of the given wire R = 



ohm. 



Ex. No. 15 



Date 



MAPPING OF MAGNETIC FIELD 
Aim: 

To map the magnetic lines offeree when the bar magnet is placed with its north 
pole facing geographic north 

Apparatus required: 

Drawing board, drawing pins, bar magnet, small magnetic compass needle and 
white sheet. 

Procedure: 

A sheet of paper is fixed on a drawing board. Using a compass needle, the 
magnetic meridian is drawn on it. A bar magnet is placed on the magnetic me- 
ridian such that its north pole points towards geographic north. The north and 
south poles of the compass are marked by pencil dots. The compass needle is 
shifted and placed so that its south pole touches the pencil dot marked for the 
north pole. The process is repeated and a series of dots are obtained. The dots 
are joined as a smooth curve. This curve is a magnetic line offeree. In the same 
way several magnetic lines offeree are drawn around the magnet as shewn in 
figure. The magnetic lines of force is due to the combined effect of the magnetic 
field due to bar magnet and the Earth. 




Result: 



The magnetic lines offeree are maped when the bar magnet is placed with 
its north pole facing geographic north. The maped sheet is attached. 



1 



4 



Ex- No. 16 
Aim 



Date 
FOCAL LENGTH OF CONVEX LENS 



To determine the focal length of convex lens by distant object method 

Apparatus required 

The given convex lens, lens stand, white screen and meter scale 
Procedure 



f + f + f^ 
Formula : Focal length / = 



f i,f 2' /"s' ^^^ ^^^ f^^^' I^^Qths measured by focucing different distant objects. 

Distant object method 

The convex lens is mounted on the stand and is kept facing a distant object 
(may be a tree or a building). The white screen is placed behind the convex lens 
and its position is adjusted to get a clear, diminished and inverted image of the 
object. The distance between the convex lens and the screen is measured. This 
gives an approximate value of the focal length of the convex lens. 

Parallel rays from distant object 




Image -^ 



Lens 



S.No 


Distant object 


Distance between the 
convex lens and the screen 


1 


Tree 


fi 


2 


Building 


fz 


3 


Electric pole 


fs 




Mean = 





Result: 



Focal length of the given convex lens f = 



-cm